DOI: 10.1148/rg.253045030
RadioGraphics 2005;25:763-786
© RSNA, 2005
Imaging-guided Percutaneous Biopsy of Mediastinal Lesions: Different Approaches and Anatomic Considerations1
Sanjay Gupta, MD,
Karen Seaberg, MD,
Michael J. Wallace, MD,
David C. Madoff, MD,
Frank A. Morello, MD, Jr,
Kamran Ahrar, MD,
Ravi Murthy, MD and
Marshall E. Hicks, MD
1 From the Department of Diagnostic Radiology, Unit 325, University of Texas M. D. Anderson Cancer Center, 1515 Holcombe Blvd, Houston, TX 77030. Recipient of a Magna Cum Laude award for an education exhibit at the 2003 RSNA Scientific Assembly. Received March 9, 2004; revision requested June 4 and received July 21; accepted August 27. All authors have no financial relationships to disclose.
Address correspondence to S.G. (e-mail: sgupta{at}mdanderson.org).
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Abstract
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Percutaneous needle biopsy with imaging guidance allows access to lesions in virtually all mediastinal locations. A direct mediastinal approach, which enables extrapleural needle placement, is the preferred method to avoid the risk of pneumothorax. Techniques that allow extrapleural access include the parasternal, paravertebral, transsternal, and suprasternal approaches, which are performed with computed tomographic or ultrasonographic guidance. The parasternal approach is used for biopsy of anterior or middle mediastinal lesions when the lesion or intervening mediastinal fat extends to the anterior chest wall, lateral to the sternum; injury to the internal mammary vessels is a potential complication. The paravertebral approach is used for biopsy of subcarinal and other posterior mediastinal lesions; saline solution is often injected to widen the mediastinum. The transsternal approach, which involves needle placement through the sternum, is used for biopsy of anterior or middle mediastinal lesions that are not accessible with the parasternal approach. Biopsy of superior mediastinal lesions can be performed with a suprasternal approach. An alternative to these direct mediastinal approaches involves advancing the needle through a pleural space created by an existing pleural effusion or iatrogenic pneumothorax. Another alternative is the transpulmonary approach, which involves transgression of the lung and visceral pleura by the needle and is associated with a substantial risk of pneumothorax.
© RSNA, 2005
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Introduction
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Imaging-guided percutaneous needle biopsy of mediastinal masses is a safe and effective technique for obtaining tissue diagnoses (1–3). Percutaneous mediastinal biopsies are usually performed with computed tomographic (CT) and ultrasonographic (US) guidance because these modalities allow precise localization and documentation of the biopsy needle and target lesion. However, the presence of major vessels, bones, the lung, and the trachea often precludes a direct approach to mediastinal lesions. Different techniques performed with CT and US guidance have been advocated for percutaneous needle biopsy of mediastinal lesions (4–13).
This article reviews the various approaches used for imaging-guided mediastinal biopsy and discusses the anatomic and technical aspects, advantages, limitations, and complications of each technique. Specific topics discussed are alternative invasive techniques, patient preparation and lesion localization, needle selection and pathologic considerations, extrapleural or direct mediastinal approaches (the parasternal, paravertebral, transsternal, suprasternal, and subxiphoid approaches), the approach through the pleural space, and the transpulmonary approach.
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Alternative Invasive Techniques for Tissue Diagnosis of Mediastinal Lesions
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In addition to percutaneous transthoracic needle biopsy, there are several alternative methods for obtaining tissue samples for cytologic or histologic diagnosis of mediastinal lesions. These include surgical techniques such as thoracoscopy, cervical mediastinoscopy, extended cervical mediastinoscopy, and anterior mediastinotomy and needle biopsy techniques such as transbronchial needle biopsy and endoscopic US–guided fine-needle aspiration biopsy (2,14–16).
Transbronchial biopsy, performed during flexible bronchoscopy, can be used to obtain fine-needle aspirates or small core samples from enlarged subcarinal and paratracheal lymph nodes. A major limitation of this approach is the inability to visualize the lymph node and the needle tip during sampling. The reported sensitivity of transbronchial mediastinal biopsy for staging non–small cell lung cancer is between 25% and 81% (14). Although the use of CT guidance and transbronchial US guidance may help improve the yield of transbronchial needle biopsy, experience with these techniques is still limited (17,18). Transbronchial needle biopsy is generally used in patients with endobronchial lesions associated with enlarged lymph nodes adjacent to the airways, as both lesions can be sampled during the same procedure.
Endoscopic US–guided needle biopsy allows access to the lower paratracheal, subcarinal, aortopulmonary, and paraesophageal regions. The advantages of endoscopic US–guided biopsy include the ability to monitor the biopsy in real time, decreased risk of pneumothorax, and a high diagnostic yield. The reported sensitivity of endoscopic US–guided biopsy in the mediastinum is 82%–96% (14,15). However, anterior lymph nodes, including those in the pretracheal and high right paratracheal regions, are not accessible because of interposition of air-filled trachea.
Cervical mediastinoscopy has traditionally been accepted as the standard of reference for preoperative staging in the mediastinum in patients with non–small cell lung carcinoma and is especially useful in patients in whom multiple mediastinal nodes need to be sampled for accurate staging. It allows direct visualization and sampling of pretracheal, paratracheal, and anterior subcarinal lymph nodes and is reported to yield a diagnosis in 83%– 89% of patients with lung cancer (2,14,15). However, the aortopulmonary, retrotracheal, posterior subcarinal, and inferior mediastinal lymph nodes are inaccessible with mediastinoscopy. Also, mediastinoscopy requires general anesthesia and may be associated with complications in 1%–3% of patients. The reported complications include vascular injury, esophageal perforation, tracheobronchial injury, mediastinitis, chylothorax, pericardial rupture, pneumothorax, and phrenic nerve injury; arrhythmias as well as death from stroke have also been reported. Extended cervical mediastinoscopy, anterior mediastinotomy, and thoracoscopy are alternative surgical techniques that can be used to assess mediastinal regions not accessible with standard mediastinoscopy.
Percutaneous transthoracic needle biopsy performed with image guidance allows access to virtually all mediastinal regions, including those that are inaccessible with mediastinoscopy, transbronchial biopsy, and endoscopic US–guided biopsy. The accuracy of transthoracic biopsy in the diagnosis of mediastinal lesions ranges from 75% to 90% (2,14,15). Transthoracic biopsy is less invasive than mediastinoscopy and requires only local anesthesia. A major limitation of this technique is the risk of pneumothorax, reported to occur in 10%– 60% of cases. Various techniques, such as the administration of saline, changes in patient position, "iatrogenic pneumothorax," and use of transsternal and suprasternal approaches, can help substantially decrease the pneumothorax rate. Another limitation of this approach is that a negative needle biopsy result does not definitively rule out malignancy and may require a repeat biopsy or mediastinoscopy for further evaluation, especially in patients with lung cancer.
The approach to a biopsy of a mediastinal lesion in a given patient depends on multiple factors, including the clinical circumstances, the location and size of the target lesion, the presence of any comorbid conditions, the availability of a procedure at the institution, and the experience of the performing physicians.
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Patient Preparation and Lesion Localization: General Considerations
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The prothrombin time, partial thromboplastin time, and platelet count are obtained to exclude any bleeding disorder before the biopsy. Although biopsies can be performed without intravenous sedation, we perform all mediastinal biopsies after induction of conscious sedation by using midazolam and fentanyl citrate and administration of local anesthesia with continuous pulse oximetry and noninvasive blood pressure monitoring.
Patients are positioned in the supine, prone, or lateral decubitus position depending on the lesion location and the biopsy approach. For CT-guided procedures, preliminary 3- or 5-mm-thick contiguous axial sections are obtained to confirm the location of the target lesion and to determine the optimal entry site of the needle. Nonenhanced CT alone is sufficient for safe biopsy planning in most patients who have previously undergone diagnostic contrast-enhanced CT or magnetic resonance imaging. However, occasionally, intravenous contrast agent administration may be required during the procedure to help define the mediastinal vessels in the projected needle path and differentiate vessels from lymph nodes. For US-guided procedures, a preliminary diagnostic US study is performed to localize the lesion and to identify a safe path for needle placement. A 3.5–7.5-MHz convex or sector transducer can be used, depending on the thickness of soft tissues and the depth of the target lesion from the skin. Color Doppler imaging may be required to identify and avoid major vessels.
The patients are observed for 1–3 hours after the procedure to ensure their hemodynamic stability and to monitor their respiratory status. The procedures are usually performed on an outpatient basis. Expiratory chest radiographs are obtained immediately and 3 hours after the biopsy in patients in whom the needle transgresses a pleural surface during the biopsy procedure.
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Needle Selection and Pathologic Considerations
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A variety of needles differing in caliber and mechanism of sample acquisition are available. Biopsy needles can be classified as small-caliber (20–25 gauge) or large-caliber (14–19 gauge) needles and as aspiration or cutting needles. Aspiration needles are 20–23-gauge needles that provide specimens suitable for cytologic evaluation. Cutting needles provide core specimens for histologic evaluation and are available in various calibers ranging from 14 to 20 gauge. Both fine-needle aspiration biopsy (FNAB) and core biopsy are well-accepted techniques for obtaining diagnostic tissue material from mediastinal lesions. Needle selection in any given case depends on a number of factors, including the size and location of the target lesion, intervening structures in the planned biopsy path, the experience and the preference of the interventional radiologist, the availability of on-site cytopathologists for immediate assessment, the suspected likely diagnosis, and the estimated amount of tissue needed for diagnosis.
FNAB of the mediastinum performed with 20-or 22-gauge needles has a high diagnostic accuracy for epithelial metastatic disease, with a reported sensitivity ranging from 84% to 100% (2,19). FNAB is also useful for diagnostic aspiration of fluid from cystic lesions. Despite recent advances in cytopathologic techniques, such as cytospin preparations, flow cytometry, immunohistochemical phenotyping, and gene rearrangement studies, the role of FNAB in the diagnosis and staging of lymphoma remains controversial. In general, although FNAB is considered adequate for staging and detection of recurrent or residual disease following treatment, core biopsy remains the preferred choice for initial lymphoma diagnosis and typing. Although the reported sensitivity of FNAB for lymphoma ranges from 42% to 82%, core biopsy allows correct diagnosis of mediastinal lymphoma in up to 91% of cases (2,20). Core biopsies are also preferred for other histologic tumor types, such as thymoma, germ cell tumors, neurogenic tumors, and benign tumors.
The small-caliber (18–20 gauge) automated cutting needles now available consistently provide high-quality histopathologic specimens adequate for histologic diagnosis in most cases, without increasing the complication rate. Several investigators have described the use of larger (14–16 gauge) cutting needles for mediastinal biopsies in selected patients (21). However, large-caliber needles should not be used if the projected needle path involves transgression of lung tissue, when the lesions are located adjacent to great vessels, or when highly vascular lesions are suspected.
Percutaneous mediastinal biopsies can be performed with the single-needle or the coaxial needle technique. The single-needle technique involves making multiple passes and using a new needle for each pass. The disadvantages of this technique are the need for image guidance for needle localization for each pass, resulting in a long procedure time, and the need to traverse intervening structures with each pass, increasing the risk of complications. The coaxial technique, which involves initial placement of a guide needle close to the target lesion followed by advancement of the biopsy needle through this needle to obtain tissue samples, is the most commonly used technique for mediastinal biopsies. In our practice, we use an 18-gauge thin-wall needle as the guide needle, through which we advance a 20–22-gauge needle for obtaining fine-needle aspirates for cytologic analysis. If indicated, 20-gauge core biopsies can also be performed for histologic evaluation through the same guide needle.
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Extrapleural or Direct Mediastinal Approaches
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A direct mediastinal approach involves placement of the biopsy needle through an extrapleural space medial to the lung to avoid transgression of the lung and pleura. The needle can be advanced through or lateral to the sternum, through the posterior paravertebral space, through the suprasternal notch, or through the subxiphoid space.
Parasternal Approach
Imaging Guidance.—
Mediastinal biopsies performed by using the parasternal approach are usually performed with CT guidance. However, US guidance can also be used for biopsy of anterior mediastinal lesions that extend to the anterior parasternal chest wall (11). The advantages of US guidance include the real-time, continuous monitoring of the needle during advancement and sampling; the availability of oblique needle paths; and the ability to perform the biopsy at the bedside of critically ill patients or to have patients with dyspnea who cannot tolerate a supine position in semi-sitting positions during the biopsy.
Anatomic and Technical Considerations.—
In the parasternal approach, the needle is inserted lateral to the sternum and advanced through the parasternal muscles and mediastinal fat into the target lesion (Fig 1). CT scans are obtained between incremental needle advancements to check the trajectory of the needle and ensure that the internal mammary vessels are not in the needle path. The internal mammary arteries and veins are located on either side of the sternum, approximately 1.3 cm from its edge; the arteries are usually situated lateral to the vein. However, there can be significant variation in the position of the vessels, and the distance from the edge of the sternum can range from 0.42 to 1.66 cm for the medial vessels and from 0.98 to 2.42 cm for the lateral vessels (22). Three internal mammary vessels (two veins and one artery) can be seen in approximately 20% of patients. These vessels can be easily identified on the CT scans of most patients, even without intravenous administration of a contrast medium, and should be looked for when planning the needle path for a parasternal biopsy. Injury to the internal mammary vessels can be avoided by selecting a path that passes immediately adjacent to the sternum and medial to the vessels (Fig 2). Alternatively, if the lesion or mediastinal fat is in contact with the anterior chest wall lateral to the internal mammary vessels, the needle can be advanced lateral to the vessels (Fig 2b).
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Figure 1. Drawing of a transverse section through the thorax at the level of the aortic arch shows the parasternal approach. The needles are inserted lateral to the sternum (ST) and advanced into the mediastinal masses (M).
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Figure 2a. Parasternal approach. (a) CT scan shows a biopsy needle (arrow) advanced between the lateral edge of the sternum and the internal mammary vessels (arrowhead) for biopsy of an anterior mediastinal mass (M) in direct contact with the chest wall. (b) CT scan shows an anterior mediastinal mass (M) in direct contact with the chest wall, lateral to the internal mammary vessels (arrowhead). The biopsy needle (arrow) passes lateral to the vessels. (c) CT scan shows a biopsy needle (arrow) advanced medial to the internal mammary vessels (arrowhead), through the mediastinal fat, and into an aortopulmonary window node (N). (d) CT scan shows a biopsy needle (arrow) advanced between the right brachiocephalic vein (V) and artery (A) for biopsy of a pretracheal mass (M).
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Figure 2b. Parasternal approach. (a) CT scan shows a biopsy needle (arrow) advanced between the lateral edge of the sternum and the internal mammary vessels (arrowhead) for biopsy of an anterior mediastinal mass (M) in direct contact with the chest wall. (b) CT scan shows an anterior mediastinal mass (M) in direct contact with the chest wall, lateral to the internal mammary vessels (arrowhead). The biopsy needle (arrow) passes lateral to the vessels. (c) CT scan shows a biopsy needle (arrow) advanced medial to the internal mammary vessels (arrowhead), through the mediastinal fat, and into an aortopulmonary window node (N). (d) CT scan shows a biopsy needle (arrow) advanced between the right brachiocephalic vein (V) and artery (A) for biopsy of a pretracheal mass (M).
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Figure 2c. Parasternal approach. (a) CT scan shows a biopsy needle (arrow) advanced between the lateral edge of the sternum and the internal mammary vessels (arrowhead) for biopsy of an anterior mediastinal mass (M) in direct contact with the chest wall. (b) CT scan shows an anterior mediastinal mass (M) in direct contact with the chest wall, lateral to the internal mammary vessels (arrowhead). The biopsy needle (arrow) passes lateral to the vessels. (c) CT scan shows a biopsy needle (arrow) advanced medial to the internal mammary vessels (arrowhead), through the mediastinal fat, and into an aortopulmonary window node (N). (d) CT scan shows a biopsy needle (arrow) advanced between the right brachiocephalic vein (V) and artery (A) for biopsy of a pretracheal mass (M).
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Figure 2d. Parasternal approach. (a) CT scan shows a biopsy needle (arrow) advanced between the lateral edge of the sternum and the internal mammary vessels (arrowhead) for biopsy of an anterior mediastinal mass (M) in direct contact with the chest wall. (b) CT scan shows an anterior mediastinal mass (M) in direct contact with the chest wall, lateral to the internal mammary vessels (arrowhead). The biopsy needle (arrow) passes lateral to the vessels. (c) CT scan shows a biopsy needle (arrow) advanced medial to the internal mammary vessels (arrowhead), through the mediastinal fat, and into an aortopulmonary window node (N). (d) CT scan shows a biopsy needle (arrow) advanced between the right brachiocephalic vein (V) and artery (A) for biopsy of a pretracheal mass (M).
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When extrapleural parasternal contact is lacking in patients in the supine position, lateral decubitus positioning may occasionally shift the mediastinum laterally and bring the lesion or the mediastinal fat into direct contact with the parasternal chest wall (2,5) (Fig 3). An injection of saline solution or dilute contrast medium can widen the mediastinum and create an artificial extrapleural path for needle placement (9) (Fig 4). Under CT guidance, a 22-gauge needle is advanced into the extrapleural space and the saline solution is injected to displace the pleura. After creation of a safe extrapleural window, the 22-gauge needle is removed and a large-bore (18-gauge or larger) guide needle is advanced through the "salinoma" up to the lesion. Subsequently, by using a coaxial technique, fine-needle aspiration and core biopsies are performed through the guide needle. Alternatively, a 22-gauge needle with a removable hub can be used for initial localization, allowing advancement of the guide needle over the 22-gauge needle.
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Figure 3a. Drawings show use of lateral decubitus positioning for the parasternal approach. M = mass, ST = sternum. (a) When the patient is in the supine position, aerated lung tissue is interposed between the mass and the chest wall. (b) When the patient is placed in the left lateral decubitus position, the mediastinum shifts to the left, creating a direct mediastinal window for needle placement.
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Figure 3b. Drawings show use of lateral decubitus positioning for the parasternal approach. M = mass, ST = sternum. (a) When the patient is in the supine position, aerated lung tissue is interposed between the mass and the chest wall. (b) When the patient is placed in the left lateral decubitus position, the mediastinum shifts to the left, creating a direct mediastinal window for needle placement.
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Figure 4a. Artificial widening of the mediastinum for the parasternal approach. (a) CT scan shows an anterior mediastinal mass (M) and a narrow parasternal mediastinal window (arrowhead). The needle (arrow) has been placed in the soft tissues. (b) CT scan obtained after injection of saline solution shows a widened mediastinum (arrowhead), which allows extrapleural placement of the biopsy needle (arrow).
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Figure 4b. Artificial widening of the mediastinum for the parasternal approach. (a) CT scan shows an anterior mediastinal mass (M) and a narrow parasternal mediastinal window (arrowhead). The needle (arrow) has been placed in the soft tissues. (b) CT scan obtained after injection of saline solution shows a widened mediastinum (arrowhead), which allows extrapleural placement of the biopsy needle (arrow).
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For a US-guided parasternal biopsy (Fig 5), the parasternal access window should be large enough to allow space for the transducer face and for simultaneous needle placement. Because of the small size of the access window, a small-footprint transducer is used, and a freehand technique is preferred over needle-attachment guides. It is essential to identify and avoid the major mediastinal vessels including the internal mammary vessels; if needed, color Doppler imaging can be used for this purpose (11).
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Figure 5a. Parasternal approach with US guidance. (a) CT scan shows an anterior mediastinal mass (M) anterior to the ascending aorta (A). (b) Transverse sonogram shows a biopsy needle (curved arrow) advanced lateral to the internal mammary vessels (straight arrow) and into the mass (M), which is anterior to the aorta (A) and right pulmonary artery (PA). Note the location of the sternum (white arrowheads) and the echogenic margin of the right lung (black arrowheads).
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Figure 5b. Parasternal approach with US guidance. (a) CT scan shows an anterior mediastinal mass (M) anterior to the ascending aorta (A). (b) Transverse sonogram shows a biopsy needle (curved arrow) advanced lateral to the internal mammary vessels (straight arrow) and into the mass (M), which is anterior to the aorta (A) and right pulmonary artery (PA). Note the location of the sternum (white arrowheads) and the echogenic margin of the right lung (black arrowheads).
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Target Lesions.—
The parasternal approach is appropriate for biopsy of an anterior or middle mediastinal lesion when the lesion itself or the intervening mediastinal fat is in direct contact with the anterior chest wall, lateral to the sternum. Although the parasternal approach is used mostly for needle biopsy of prevascular lesions (Fig 2a, 2b) or masses in the aortopulmonary window (Fig 2c), it can also occasionally be used for pretracheal or paratracheal lesions. The needle can be advanced between the major vessels for biopsy of pre- or paratracheal lesions that do not extend up to the anterior chest wall (Fig 2d). Transgression of the brachiocephalic veins or superior vena cava with thin (eg, 22-gauge) needles for biopsy of middle mediastinal lesions has been reported, without complications (3,7,12).
Limitations and Complications.—
Occasionally, the space between the lateral edge of the sternum and the internal mammary vessels may be too small to allow safe parasternal needle placement. Moreover, the degree of contact between the mediastinum and the parasternal chest wall may alter with breathing during the biopsy procedure, precluding the use of the parasternal approach (Fig 6) or resulting in inadvertent transgression of the lung or pleural space (Fig 7). Breathing can also cause a small mediastinal lesion to move out of the biopsy plane (Fig 6). An inadequate acoustic window and poor lesion visualization can be problems when a US-guided parasternal approach is used for mediastinal biopsy; thus, the use of this approach is limited to biopsy of large anterior mediastinal lesions. In addition, curvature of the anterior ribs or costal cartilage may not allow enough space for the US probe and the biopsy needle. The parasternal approach has the potential risk of accidental puncture of the internal mammary vessels, which can occasionally result in substantial extrapleural and pleural hemorrhage (23) (Fig 8).
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Figure 6a. Effect of breathing on the mediastinum. (a) CT scan shows the needle (arrow) in a parasternal location, a small anterior mediastinal lesion (arrowhead), and a potential extrapleural window. (b) CT scan obtained a few seconds later shows interposition of the lung in the path of the biopsy needle (arrow); this interposition is caused by variation in respiration and precludes extrapleural biopsy. Note that the target lesion is no longer seen in the biopsy plane.
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Figure 6b. Effect of breathing on the mediastinum. (a) CT scan shows the needle (arrow) in a parasternal location, a small anterior mediastinal lesion (arrowhead), and a potential extrapleural window. (b) CT scan obtained a few seconds later shows interposition of the lung in the path of the biopsy needle (arrow); this interposition is caused by variation in respiration and precludes extrapleural biopsy. Note that the target lesion is no longer seen in the biopsy plane.
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Figure 7a. Inadvertent transgression of the pleura. (a) CT scan shows a biopsy needle (arrow) passed through the mediastinal fat toward a lesion (M), which is anterior to the pulmonary artery (PA). (b) CT scan shows air in the path of the needle. The air is associated with collapse of the lung (arrows), which has caused separation of the mediastinal fat from the anterior chest wall. (c) Drawing shows how interposition of the parietal pleura (arrow) in the path of the needle can result in inadvertent transgression of the pleural space during parasternal biopsy. M = mass, ST = sternum.
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Figure 7b. Inadvertent transgression of the pleura. (a) CT scan shows a biopsy needle (arrow) passed through the mediastinal fat toward a lesion (M), which is anterior to the pulmonary artery (PA). (b) CT scan shows air in the path of the needle. The air is associated with collapse of the lung (arrows), which has caused separation of the mediastinal fat from the anterior chest wall. (c) Drawing shows how interposition of the parietal pleura (arrow) in the path of the needle can result in inadvertent transgression of the pleural space during parasternal biopsy. M = mass, ST = sternum.
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Figure 7c. Inadvertent transgression of the pleura. (a) CT scan shows a biopsy needle (arrow) passed through the mediastinal fat toward a lesion (M), which is anterior to the pulmonary artery (PA). (b) CT scan shows air in the path of the needle. The air is associated with collapse of the lung (arrows), which has caused separation of the mediastinal fat from the anterior chest wall. (c) Drawing shows how interposition of the parietal pleura (arrow) in the path of the needle can result in inadvertent transgression of the pleural space during parasternal biopsy. M = mass, ST = sternum.
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Figure 8a. Injury to the internal mammary artery. (a) CT scan shows a biopsy needle that was advanced parasternally (arrow), causing a mediastinal hematoma (arrowhead) secondary to injury to the internal mammary vessels. (b) Postprocedure CT scan shows enlargement of the mediastinal hematoma (arrowheads) and a left hemothorax (arrows).
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Figure 8b. Injury to the internal mammary artery. (a) CT scan shows a biopsy needle that was advanced parasternally (arrow), causing a mediastinal hematoma (arrowhead) secondary to injury to the internal mammary vessels. (b) Postprocedure CT scan shows enlargement of the mediastinal hematoma (arrowheads) and a left hemothorax (arrows).
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Paravertebral Approach
Imaging Guidance.—
Mediastinal biopsies that use a paravertebral approach are performed with CT guidance.
Anatomic and Technical Considerations.—
For the paravertebral approach, the patient is placed in the prone or prone oblique position; a lateral decubitus position can be used in patients who are unable to lie prone. The needle is advanced immediately lateral to the vertebral body between the endothoracic fascia and the parietal pleura (Fig 9). The endothoracic fascia, located outside the parietal pleura, lines the walls of the thorax and merges with the prevertebral fascia posteromedially. In some patients, the paravertebral extrapleural space may be wide enough to allow needle biopsy without traversing the pleura. However, in most patients, an injection of saline solution or a dilute iodinated contrast medium is required to displace the mediastinal parietal pleura to gain extrapleural access (5,9).
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Figure 9. Drawing shows the extrapleural paravertebral approach for needle biopsy of a posterior mediastinal mass (M) after widening of the mediastinal space by injection of saline solution (Fl).
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An 18-gauge blunt-tip needle or cannula is used for creation of the extrapleural space; the same needle can be used as the guide needle for performing the biopsy with a coaxial technique (Fig 10). Some authors advocate using a 22-gauge needle to inject fluid and subsequently exchanging it for an 18-gauge needle to perform the biopsy (9). Injection of 10–20 mL of saline solution is usually sufficient to achieve adequate mediastinal widening; however, larger volumes may be required (24). Insufficient widening can occur when the needle tip lies outside the endothoracic fascia, in a blood vessel, or in the pleural space. The injection of saline solution also displaces mediastinal structures, such as the azygos vein, esophagus, nerves, and vertebral vessels, from the needle path. However, needle advancement and biopsy must be performed expeditiously because the mediastinal widening regresses owing to the redistribution of fluid. The needle should be advanced in a direct paravertebral path, medial to the pleural surface of the head of the ribs. A needle path lateral to the transverse process may not achieve mediastinal widening because of the fixation of the endothoracic fascia and parietal pleura at this location (5,9). The biopsy needle should be placed along the superior edge of the rib and above the transverse process to avoid injury to the intercostal nerve and artery.
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Figure 10a. Paravertebral approach for biopsy of a subcarinal mass. (a) CT scan shows a subcarinal mass (M); an 18-gauge needle has been advanced to the edge of the paravertebral space (arrowhead). (b) CT scan shows that injection of saline solution through the guide needle (arrow) has widened the mediastinum (arrowhead), creating a safe extrapleural path to the mass (M). (c) CT scan shows a 22-gauge needle (arrowhead) advanced through the 18-gauge needle (arrow) for biopsy of the mass (M).
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Figure 10b. Paravertebral approach for biopsy of a subcarinal mass. (a) CT scan shows a subcarinal mass (M); an 18-gauge needle has been advanced to the edge of the paravertebral space (arrowhead). (b) CT scan shows that injection of saline solution through the guide needle (arrow) has widened the mediastinum (arrowhead), creating a safe extrapleural path to the mass (M). (c) CT scan shows a 22-gauge needle (arrowhead) advanced through the 18-gauge needle (arrow) for biopsy of the mass (M).
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Figure 10c. Paravertebral approach for biopsy of a subcarinal mass. (a) CT scan shows a subcarinal mass (M); an 18-gauge needle has been advanced to the edge of the paravertebral space (arrowhead). (b) CT scan shows that injection of saline solution through the guide needle (arrow) has widened the mediastinum (arrowhead), creating a safe extrapleural path to the mass (M). (c) CT scan shows a 22-gauge needle (arrowhead) advanced through the 18-gauge needle (arrow) for biopsy of the mass (M).
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Target Lesions.—
The paravertebral approach allows access to posterior mediastinal lesions and is used mostly for biopsy of subcarinal lesions from the right side (Fig 10). Occasionally, a saline injection may cause sufficient displacement of the descending aorta to allow retroaortic access from the left side (Fig 11) for biopsy of subcarinal, periesophageal, or left paratracheal masses. The right paravertebral approach can also sometimes be used for accessing middle mediastinal lesions located in the pre- or paratracheal spaces (Fig 12).
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Figure 11a. Retroaortic paravertebral approach. (a) CT scan shows an 18-gauge guide needle (thick arrow) inserted in the paravertebral space (thin arrows) and advanced between the descending aorta (DA) and vertebral body after widening of these spaces by injection of saline solution. A 22-gauge needle was advanced through the guide needle to obtain aspirates from a subcarinal mass (M). E = esophagus. (b) CT scan shows use of coaxial 18- and 22-gauge needles (black arrow) for biopsy of a left pretracheal mass (M). Saline solution was administered to widen the paravertebral (white arrow) and retroaortic spaces.
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Figure 11b. Retroaortic paravertebral approach. (a) CT scan shows an 18-gauge guide needle (thick arrow) inserted in the paravertebral space (thin arrows) and advanced between the descending aorta (DA) and vertebral body after widening of these spaces by injection of saline solution. A 22-gauge needle was advanced through the guide needle to obtain aspirates from a subcarinal mass (M). E = esophagus. (b) CT scan shows use of coaxial 18- and 22-gauge needles (black arrow) for biopsy of a left pretracheal mass (M). Saline solution was administered to widen the paravertebral (white arrow) and retroaortic spaces.
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Figure 12a. Paravertebral approach for biopsy of a right paratracheal mass. (a) CT scan shows a right paratracheal mass (M) that lacks an extrapleural window (arrowhead). (b) CT scan shows an extrapleural window (thin arrows) created by injection of saline solution through an 18-gauge needle (thick arrow). This extrapleural window allowed safe biopsy of the mass (M) with a coaxially placed 22-gauge needle (arrowhead).
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Figure 12b. Paravertebral approach for biopsy of a right paratracheal mass. (a) CT scan shows a right paratracheal mass (M) that lacks an extrapleural window (arrowhead). (b) CT scan shows an extrapleural window (thin arrows) created by injection of saline solution through an 18-gauge needle (thick arrow). This extrapleural window allowed safe biopsy of the mass (M) with a coaxially placed 22-gauge needle (arrowhead).
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Limitations and Complications.—
The presence of osteophytes may preclude paravertebral extrapleural access (Fig 13). A narrow intercostal space and the orientation of the transverse process also may interfere with needle placement. Inadequate mediastinal widening may result in inadvertent pleural or pulmonary transgression. The paravertebral approach has the potential risk of injury to the azygos vein, paravertebral vessels, intercostal vessels and nerves, spinal nerves, vagus nerves, and esophagus. An injury to the intercostal artery may result in an extrapleural hematoma or hemothorax. Rarely reported complications include vasovagal reactions, most likely secondary to apprehension, pain, or innervation of the pleura by the pulmonary plexus; intercostal neuritis caused by injury to the intercostal nerve; and transient Horner syndrome caused by irritation or injury of the sympathetic ganglion (5,9,24). Some investigators recommend oral administration of a contrast medium if the esophagus is not identified on nonenhanced CT scans (5,9).
Transsternal Approach
Imaging Guidance.—
Transsternal biopsies are performed with CT guidance.
Anatomic and Technical Considerations.—
The transsternal approach involves needle placement through the sternal bone (Fig 14). A coaxial needle technique is used. Astrom et al (13) performed transsternal mediastinal biopsies using a large-caliber bone biopsy system comprising two cannulas, long and short drill bits, a depth gauge, and a cutting biopsy needle. However, in our experience, several common 18-gauge guide needles are adequate to penetrate the sternum. Although an 18-gauge hypodermic needle can also be used to penetrate the sternum, it precludes the insertion of a coaxial 20-gauge core biopsy needle to obtain larger specimens when needed (8).
Transsternal needle insertion performed with local anesthesia and intravenous sedation is well tolerated by patients. The infiltration of a local anesthetic on the periosteum of the anterior and posterior sternal cortices minimizes the discomfort associated with the procedure. Because patient motion may change the mediastinal topography, it is important to place the patient in a comfortable position and minimize the time required to complete the biopsy. A nonenhanced CT study performed immediately before the procedure is sufficient for safe biopsy planning in most patients who have previously undergone diagnostic contrast-enhanced CT; rarely, intravenous administration of a contrast agent may be needed during the procedure to help differentiate the mediastinal structures.
Target Lesions.—
The transsternal approach is used for biopsy of lesions that are not safely accessible with the parasternal approach. This approach is most commonly used for biopsy of anterior mediastinal masses (6,13) (Fig 15a). However, middle or posterior mediastinal masses can also be accessed with this approach (8) (Fig 15b, 15c). Small-gauge (eg, 22-gauge) needles can be advanced between vascular structures to reach these middle and posterior mediastinal masses (Fig 15c). As mentioned earlier, transgression of the brachiocephalic vein with 22-gauge needles for biopsy of middle or posterior mediastinal masses has been shown to be safe (8) (Fig 16). A curved 22-gauge Chiba needle can also be used to compensate for minor discrepancies in the needle trajectory (8).
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Figure 15a. Transsternal approach. (a) CT scan shows an 18-gauge needle (arrow) traversing the sternum and a 20-gauge core biopsy needle (arrowhead), which was advanced through the 18-gauge needle into an anterior mediastinal mass (M). (b) CT scan shows an 18-gauge biopsy needle (arrow) advanced through the sternum into an aortopulmonary window mass (M). A = ascending aorta, PA = pulmonary artery. (c) CT scan shows transsternal biopsy of a pretracheal mass (M) with an inner 22-gauge biopsy needle (arrow) passing between the superior vena cava (V) and aortic arch (A).
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Figure 15b. Transsternal approach. (a) CT scan shows an 18-gauge needle (arrow) traversing the sternum and a 20-gauge core biopsy needle (arrowhead), which was advanced through the 18-gauge needle into an anterior mediastinal mass (M). (b) CT scan shows an 18-gauge biopsy needle (arrow) advanced through the sternum into an aortopulmonary window mass (M). A = ascending aorta, PA = pulmonary artery. (c) CT scan shows transsternal biopsy of a pretracheal mass (M) with an inner 22-gauge biopsy needle (arrow) passing between the superior vena cava (V) and aortic arch (A).
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Figure 15c. Transsternal approach. (a) CT scan shows an 18-gauge needle (arrow) traversing the sternum and a 20-gauge core biopsy needle (arrowhead), which was advanced through the 18-gauge needle into an anterior mediastinal mass (M). (b) CT scan shows an 18-gauge biopsy needle (arrow) advanced through the sternum into an aortopulmonary window mass (M). A = ascending aorta, PA = pulmonary artery. (c) CT scan shows transsternal biopsy of a pretracheal mass (M) with an inner 22-gauge biopsy needle (arrow) passing between the superior vena cava (V) and aortic arch (A).
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Figure 16a. Transsternal approach. (a) Contrast-enhanced CT scan shows a retrotracheal mass (M) posterior to the right and left brachiocephalic veins (V). (b) CT scan shows a 22-gauge biopsy needle (arrowhead) coaxially introduced through an 18-gauge transsternal needle (arrow). The biopsy needle transgresses the left brachiocephalic vein (V) to obtain a sample of the mass (M).
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Figure 16b. Transsternal approach. (a) Contrast-enhanced CT scan shows a retrotracheal mass (M) posterior to the right and left brachiocephalic veins (V). (b) CT scan shows a 22-gauge biopsy needle (arrowhead) coaxially introduced through an 18-gauge transsternal needle (arrow). The biopsy needle transgresses the left brachiocephalic vein (V) to obtain a sample of the mass (M).
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Limitations and Complications.—
The sternum may be difficult to penetrate in a patient with a history of a previous sternotomy. Moreover, mediastinal movements from respiration and cardiac or aortic pulsation can result in the lesion moving in and out of the biopsy plane, particularly in cases of small masses located close to the aortic arch. The needle trajectory cannot be altered after sternal penetration without totally withdrawing the needle. Occasionally, the amount of contact between the mediastinum and the sternum may change during the biopsy, resulting in inadvertent transgression of the pleural space.
Hemorrhage, a potential complication of any mediastinal biopsy, can be prevented by careful planning of the biopsy needle trajectory based on the location of major vessels in relation to the lesion. Small mediastinal hematomas are occasionally seen after transsternal biopsies (Fig 17); they are usually asymptomatic and self-limited and do not require any treatment.
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Figure 17. Transsternal approach. CT scan shows a needle traversing the sternum during biopsy of an anterior mediastinal lesion (M). A small mediastinal hematoma (arrowhead) resulted from the biopsy.
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Suprasternal Approach
Imaging Guidance.—
Both CT and US can be used to guide mediastinal biopsies performed with the suprasternal approach. The major advantages of using US guidance with this approach are its multiplanar imaging capability, allowing use of combined angled approaches for needle placement in the craniocaudal and mediolateral planes (which would not be possible with CT guidance), and the ability to continuously monitor the needle tip relative to the lesion and the major vessels (7).
Anatomic and Technical Considerations.—
In the suprasternal approach, the needle is inserted through the suprasternal fossa and advanced in a caudal direction toward the target lesion (Fig 18). Two methods have been described for CT-guided mediastinal biopsies performed with the suprasternal approach: One involves placing the patient in a semi-erect position supported by pillows, with the patient’s head turned to the side. The CT gantry is angulated in the craniocaudal plane and direct semicoronal images are obtained, allowing direct visualization of the projected needle path between the skin and the lesion (5) (Fig 19). The guide needle is inserted along the plane of the angled CT gantry by using the gantry light to correctly guide the needle angulation. CT scans obtained with the gantry in the tilted position allow visualization of the entire length of the needle. When the trajectory and position of the guide needle are considered satisfactory, a biopsy needle of an appropriate caliber and length is advanced coaxially through the guide needle into the lesion.
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Figure 18a. Suprasternal approach. (a) Drawing (sagittal oblique view) shows the suprasternal approach for biopsy of a superior mediastinal mass (M). ST = sternum. (b) Drawing (coronal oblique view) shows the suprasternal approach for biopsy of a mediastinal mass (M).
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Figure 18b. Suprasternal approach. (a) Drawing (sagittal oblique view) shows the suprasternal approach for biopsy of a superior mediastinal mass (M). ST = sternum. (b) Drawing (coronal oblique view) shows the suprasternal approach for biopsy of a mediastinal mass (M).
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Figure 19a. Suprasternal approach with semicoronal scanning. (a) Axial CT scan shows a bilobular retrosternal mediastinal mass (M) between the right brachiocephalic vein (V) and artery (A). (b) Semicoronal CT scan, obtained by placing a pillow under the patient’s shoulders and tilting the CT gantry craniocaudally, shows a direct suprasternal access window, which allows safe placement of a biopsy needle (arrow) into the mass (M). A = brachiocephalic artery, V = right brachiocephalic vein.
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Figure 19b. Suprasternal approach with semicoronal scanning. (a) Axial CT scan shows a bilobular retrosternal mediastinal mass (M) between the right brachiocephalic vein (V) and artery (A). (b) Semicoronal CT scan, obtained by placing a pillow under the patient’s shoulders and tilting the CT gantry craniocaudally, shows a direct suprasternal access window, which allows safe placement of a biopsy needle (arrow) into the mass (M). A = brachiocephalic artery, V = right brachiocephalic vein.
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In the second method, patients undergo the biopsy in the supine position, with the neck hyperextended. Contiguous axial CT scans are obtained from the suprasternal level to the level of the target lesion. By using a triangulation method, the lesion depth from the skin entry site, the angle of incidence, and the anteroposterior and mediolateral inclination of the needle are estimated. The needle path corresponds to the hypotenuse of a right triangle, with the other two sides represented by the lesion depth and the craniocaudal distance between the axial level of the lesion and that of the skin entry site (Fig 20a). The needle is advanced with CT guidance (4), and axial CT scans are obtained to check the position of the needle tip (Fig 20).
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Figure 20a. Suprasternal approach with the triangulation method. (a) Schematic drawing shows the triangulation method (25). Z represents the point on the skin in the same transaxial plane as the target lesion (M). C or the depth of needle insertion is calculated with the Pythagorean theorem (A2 + B2 = C2). The angle of needle insertion (a) is equal to the angle  , which is calculated by means of the tangent B/A. ST = sternum. (b) Axial CT scan shows an anterior mediastinal mass (M) located behind the sternum. (c) Axial CT scan shows the tip of the biopsy needle (arrow) in the mass (M). The needle was inserted through the suprasternal notch and angled downward.
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Figure 20b. Suprasternal approach with the triangulation method. (a) Schematic drawing shows the triangulation method (25). Z represents the point on the skin in the same transaxial plane as the target lesion (M). C or the depth of needle insertion is calculated with the Pythagorean theorem (A2 + B2 = C2). The angle of needle insertion (a) is equal to the angle , which is calculated by means of the tangent B/A. ST = sternum. (b) Axial CT scan shows an anterior mediastinal mass (M) located behind the sternum. (c) Axial CT scan shows the tip of the biopsy needle (arrow) in the mass (M). The needle was inserted through the suprasternal notch and angled downward.
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Figure 20c. Suprasternal approach with the triangulation method. (a) Schematic drawing shows the triangulation method (25). Z represents the point on the skin in the same transaxial plane as the target lesion (M). C or the depth of needle insertion is calculated with the Pythagorean theorem (A2 + B2 = C2). The angle of needle insertion (a) is equal to the angle , which is calculated by means of the tangent B/A. ST = sternum. (b) Axial CT scan shows an anterior mediastinal mass (M) located behind the sternum. (c) Axial CT scan shows the tip of the biopsy needle (arrow) in the mass (M). The needle was inserted through the suprasternal notch and angled downward.
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For US-guided procedures, a small-footprint transducer, which permits easy placement in the suprasternal notch and leaves enough room for simultaneous placement of the biopsy needle, is necessary. A 3.5-MHz or higher-frequency (5–7.5-MHz) transducer may be used, depending on the depth of the target lesion from the suprasternal notch (7,11). The patient is placed in a supine position with pillows under the shoulder to keep the neck hyperextended. Because of limited space, a freehand technique is preferred over needle-attachment guides.
Anterior mediastinal lesions that are large enough to extend above the cranial edge of the manubrium can be directly accessed (Fig 21). However, in most patients, the lesions are hidden behind the sternum. In these cases, the transducer is positioned in the notch and angled downward to scan the mediastinum in various sagittal and coronal oblique planes to locate the lesion and identify a safe, avascular route for needle placement. The soft tissues around the trachea and great vessels provide an adequate acoustic window, and the large arteries and veins are anatomic guides for orientation in the superior mediastinum (Fig 22). For pre- or paratracheal lesions, the needle is advanced between the vessels to reach the lesion. As with other approaches, transgression of the brachiocephalic vein with thin (22-gauge) needles is generally considered safe (7). Occasionally, a small-caliber needle may be advanced through the thyroid to sample a retrotracheal lesion (Fig 23).
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Figure 21a. Suprasternal approach with US guidance. (a) CT scan shows a right paratracheal mass (M) that extends above the level of the manubrium. (b) Semicoronal sonogram obtained through the suprasternal window shows the needle (arrow) within the mass (M).
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Figure 21b. Suprasternal approach with US guidance. (a) CT scan shows a right paratracheal mass (M) that extends above the level of the manubrium. (b) Semicoronal sonogram obtained through the suprasternal window shows the needle (arrow) within the mass (M).
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Figure 22a. Suprasternal approach with US guidance. (a) CT scan shows an anterior mediastinal mass (M) located behind the sternum and anterior to the arteries arising from the aorta. (b) Suprasternal sonogram (semicoronal view) shows the mass (M) anterosuperior to the arteries (A). (c) Suprasternal sonogram (semicoronal view) shows the biopsy needle (arrow), which has been advanced into the mass (M) under US guidance.
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Figure 22b. Suprasternal approach with US guidance. (a) CT scan shows an anterior mediastinal mass (M) located behind the sternum and anterior to the arteries arising from the aorta. (b) Suprasternal sonogram (semicoronal view) shows the mass (M) anterosuperior to the arteries (A). (c) Suprasternal sonogram (semicoronal view) shows the biopsy needle (arrow), which has been advanced into the mass (M) under US guidance.
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Figure 22c. Suprasternal approach with US guidance. (a) CT scan shows an anterior mediastinal mass (M) located behind the sternum and anterior to the arteries arising from the aorta. (b) Suprasternal sonogram (semicoronal view) shows the mass (M) anterosuperior to the arteries (A). (c) Suprasternal sonogram (semicoronal view) shows the biopsy needle (arrow), which has been advanced into the mass (M) under US guidance.
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Figure 23a. Suprasternal approach with US guidance. (a) CT scan shows a retrotracheal mass (M). (b) Suprasternal sonogram (semicoronal view) shows a biopsy needle (arrow) that has traversed the thyroid gland (T) on its way to the mass (M).
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Figure 23b. Suprasternal approach with US guidance. (a) CT scan shows a retrotracheal mass (M). (b) Suprasternal sonogram (semicoronal view) shows a biopsy needle (arrow) that has traversed the thyroid gland (T) on its way to the mass (M).
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Target Lesions.—
The suprasternal fossa offers an extrapleural window for access to the superior mediastinum. Thus, masses in the superior mediastinum located above the level of the aortic arch can be accessed with a suprasternal approach. This approach can been used for biopsy of prevascular, pretracheal, and paratracheal lesions and lesions in the aortopulmonary window (4,5,7,11,12).
Limitations and Complications.—
Angled suprasternal approaches performed with CT guidance by using a gantry tilt or semicoronal route require excellent patient cooperation. The triangulation method involves contiguous localization scans to measure the distance between the lesion and the entry site, complex calculations of the degree of inclination needed to direct the needle into the lesion, and multiple-level scanning to check the position of the needle tip during its advancement and before aspiration, and this method can be time-consuming and cumbersome. An inadequate acoustic window is a frequent problem with US guidance, limiting its use to biopsy of large anterior or middle mediastinal lesions located above the level of the aortic arch. US detection of small lesions situated immediately posterior to the sternum is also restricted. Apart from the occasional episode of vasovagal reaction, major complications are rare.
Subxiphoid Approach
A subxiphoid approach can occasionally be used for biopsy of mediastinal masses. Mediastinal biopsy with the subxiphoid approach can be performed under CT and US guidance. With this approach, the needle is inserted below the xiphoid process of the sternum and is angled cranially. This approach allows biopsy of anterior pericardial lymph nodes and other pericardial masses. This approach can also be used for biopsy of posterior mediastinal masses by advancing the needle through the liver in a cranial direction (Fig 24). Sonography performed with the transducer placed in the subxiphoid region and angled cranially allows visualization of posterior mediastinal lesions through the liver.
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Figure 24a. Subxiphoid approach. (a) CT scan shows a large mass (M) in the posterior mediastinum. (b) Semicoronal sonogram obtained by using the subxiphoid approach with the transducer angled upward shows the mass (M) posterosuperior to the left lobe of the liver (L). The biopsy needle was advanced under US guidance. CT was performed to verify the needle trajectory. (c) CT scan shows the needle (arrow) passing through the liver (L). (d) CT scan shows the needle tip (arrow) in the mass (M).
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Figure 24b. Subxiphoid approach. (a) CT scan shows a large mass (M) in the posterior mediastinum. (b) Semicoronal sonogram obtained by using the subxiphoid approach with the transducer angled upward shows the mass (M) posterosuperior to the left lobe of the liver (L). The biopsy needle was advanced under US guidance. CT was performed to verify the needle trajectory. (c) CT scan shows the needle (arrow) passing through the liver (L). (d) CT scan shows the needle tip (arrow) in the mass (M).
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Figure 24c. Subxiphoid approach. (a) CT scan shows a large mass (M) in the posterior mediastinum. (b) Semicoronal sonogram obtained by using the subxiphoid approach with the transducer angled upward shows the mass (M) posterosuperior to the left lobe of the liver (L). The biopsy needle was advanced under US guidance. CT was performed to verify the needle trajectory. (c) CT scan shows the needle (arrow) passing through the liver (L). (d) CT scan shows the needle tip (arrow) in the mass (M).
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Figure 24d. Subxiphoid approach. (a) CT scan shows a large mass (M) in the posterior mediastinum. (b) Semicoronal sonogram obtained by using the subxiphoid approach with the transducer angled upward shows the mass (M) posterosuperior to the left lobe of the liver (L). The biopsy needle was advanced under US guidance. CT was performed to verify the needle trajectory. (c) CT scan shows the needle (arrow) passing through the liver (L). (d) CT scan shows the needle tip (arrow) in the mass (M).
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Approach through the Pleural Space
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Imaging Guidance
CT guidance is used in mediastinal biopsies performed with an approach through the pleural space. Occasionally, US guidance can also be used for accessing mediastinal lesions through large pleural effusions.
Anatomic and Technical Considerations
For biopsy of anterior, middle, or posterior mediastinal lesions, the needle can sometimes be advanced through the pleural space created by an existing pleural effusion or an iatrogenic pneumothorax (Fig 25). Free-flowing pleural fluid ipsilateral to the mediastinal mass can be made to flow into the medial pleural recess by placing the patient in the contralateral decubitus position (2,5). This repositioning results in the creation of a "pleural window" for needle placement by displacing the intervening lung parenchyma; patients with loculated pleural fluid in the medial pleural recess do not require this positional maneuver (Fig 26). The presence of pleural fluid provides an acoustic window for US visualization of mediastinal lesions, permitting use of US guidance for needle placement through the pleural fluid. US guidance is especially useful in patients with dyspnea who cannot tolerate a supine or prone position (Fig 27).
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Figure 26. Pleural space approach. CT scan shows placement of an 18-gauge needle (thick arrow) into a posterior mediastinal mass (M) through a loculated pleural effusion (thin arrows). Note the presence of free pleural fluid (PF) anteriorly.
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Figure 27a. Pleural space approach. (a) CT scan shows a large mediastinal mass (M) encasing the descending thoracic aorta (A). Note the presence of a left pleural effusion (FL). The patient was unable to maintain a supine or prone position owing to dyspnea. (b) Transverse sonogram obtained by using the posterior intercostal approach with the patient in a semisitting position shows the mass (M), pleural fluid (FL), spleen (SP), and aorta (A). The biopsy needle (arrow) has been advanced through the pleural fluid into the mass.
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Figure 27b. Pleural space approach. (a) CT scan shows a large mediastinal mass (M) encasing the descending thoracic aorta (A). Note the presence of a left pleural effusion (FL). The patient was unable to maintain a supine or prone position owing to dyspnea. (b) Transverse sonogram obtained by using the posterior intercostal approach with the patient in a semisitting position shows the mass (M), pleural fluid (FL), spleen (SP), and aorta (A). The biopsy needle (arrow) has been advanced through the pleural fluid into the mass.
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A preexisting iatrogenic pneumothorax or intentionally injected intrapleural air can also create extrapulmonary access (2,5) (Fig 28). In this procedure, an 18-gauge needle is advanced to the parietal pleura. The blunt needle cannula itself (from which the sharp stylet has been removed) or the needle with a blunt stylet is advanced through the parietal pleura and displaces the visceral pleura. Air is then injected into the pleural space to collapse the lung. The air is aspirated at the end of the biopsy procedure to reinflate the lung. This approach avoids puncture of the visceral pleura and hence is useful in patients who have severe emphysema and are at risk of developing persistent air leaks if a transpulmonary approach is used.
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Figure 28a. Pleural space approach. (a) CT scan shows a subcarinal mass (M). (b) CT scan shows an 18-gauge blunt-tip needle (black arrow) advanced through the parietal pleura, thus displacing the visceral pleura (white arrow). M = mass. (c) CT scan shows collapse of the lung (white arrows) caused by introduction of air into the pleural space. The lung collapse has allowed advancement of the biopsy needle (black arrow) through the pleural space. M = mass. The air was evacuated at the end of the biopsy procedure.
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Figure 28b. Pleural space approach. (a) CT scan shows a subcarinal mass (M). (b) CT scan shows an 18-gauge blunt-tip needle (black arrow) advanced through the parietal pleura, thus displacing the visceral pleura (white arrow). M = mass. (c) CT scan shows collapse of the lung (white arrows) caused by introduction of air into the pleural space. The lung collapse has allowed advancement of the biopsy needle (black arrow) through the pleural space. M = mass. The air was evacuated at the end of the biopsy procedure.
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Figure 28c. Pleural space approach. (a) CT scan shows a subcarinal mass (M). (b) CT scan shows an 18-gauge blunt-tip needle (black arrow) advanced through the parietal pleura, thus displacing the visceral pleura (white arrow). M = mass. (c) CT scan shows collapse of the lung (white arrows) caused by introduction of air into the pleural space. The lung collapse has allowed advancement of the biopsy needle (black arrow) through the pleural space. M = mass. The air was evacuated at the end of the biopsy procedure.
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Limitations and Complications
It may not always be possible to interpose the pleural fluid between the skin and the target lesion, especially in the presence of pleural thickening and septations. The visceral pleura may be inadvertently punctured when using an approach through the pleural space during attempts to create an iatrogenic pneumothorax, resulting in air leakage. Moreover, inaccurate placement of the blunt needle outside the parietal pleura may result in dissection of injected air into the extrapleural soft tissues (Fig 29).
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Figure 29a. Failed attempt at biopsy with the pleural space approach. M = mass. (a) CT scan shows placement of an 18-gauge needle (arrow) in what was mistakenly thought to be the pleural space. (b) CT scan shows injected air dissecting into the chest wall and mediastinal soft tissues (arrowheads) because of the inaccurate needle placement.
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Figure 29b. Failed attempt at biopsy with the pleural space approach. M = mass. (a) CT scan shows placement of an 18-gauge needle (arrow) in what was mistakenly thought to be the pleural space. (b) CT scan shows injected air dissecting into the chest wall and mediastinal soft tissues (arrowheads) because of the inaccurate needle placement.
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Transpulmonary Approach
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Imaging Guidance
CT guidance is used for transpulmonary biopsies of mediastinal masses.
Anatomic and Technical Considerations
The transpulmonary approach to mediastinal biopsy allows access to masses in various anterior, middle, and posterior mediastinal locations (2,5) (Fig 30). This approach is generally used for biopsy of lesions that are not accessible with an extrapleural approach. The patient is placed in the appropriate position for easiest access to the mediastinal lesion. The needle passes through the lung parenchyma and two layers of visceral pleura. Attempts should be made to avoid fissures, emphysematous bullae, and major intrapulmonary vessels.
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Figure 30a. Transpulmonary approach. (a) CT scan shows needle placement (arrow) for transpulmonary biopsy of a subcarinal mass (M). (b) CT scan shows needle placement (arrow) for transpulmonary biopsy of a paratracheal mass (M). (c) CT scan shows needle placement (arrow) for transpulmonary biopsy of an aortopulmonary mass (M). (d) CT scan shows needle placement (straight arrow) for transpulmonary biopsy of a right paratracheal mass (M). The presence of the superior vena cava (SVC) and azygos vein (curved arrow) precluded anterior or posterior approaches. Note the alveolar hemorrhage in the needle track (arrowheads).
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Figure 30b. Transpulmonary approach. (a) CT scan shows needle placement (arrow) for transpulmonary biopsy of a subcarinal mass (M). (b) CT scan shows needle placement (arrow) for transpulmonary biopsy of a paratracheal mass (M). (c) CT scan shows needle placement (arrow) for transpulmonary biopsy of an aortopulmonary mass (M). (d) CT scan shows needle placement (straight arrow) for transpulmonary biopsy of a right paratracheal mass (M). The presence of the superior vena cava (SVC) and azygos vein (curved arrow) precluded anterior or posterior approaches. Note the alveolar hemorrhage in the needle track (arrowheads).
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Figure 30c. Transpulmonary approach. (a) CT scan shows needle placement (arrow) for transpulmonary biopsy of a subcarinal mass (M). (b) CT scan shows needle placement (arrow) for transpulmonary biopsy of a paratracheal mass (M). (c) CT scan shows needle placement (arrow) for transpulmonary biopsy of an aortopulmonary mass (M). (d) CT scan shows needle placement (straight arrow) for transpulmonary biopsy of a right paratracheal mass (M). The presence of the superior vena cava (SVC) and azygos vein (curved arrow) precluded anterior or posterior approaches. Note the alveolar hemorrhage in the needle track (arrowheads).
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Figure 30d. Transpulmonary approach. (a) CT scan shows needle placement (arrow) for transpulmonary biopsy of a subcarinal mass (M). (b) CT scan shows needle placement (arrow) for transpulmonary biopsy of a paratracheal mass (M). (c) CT scan shows needle placement (arrow) for transpulmonary biopsy of an aortopulmonary mass (M). (d) CT scan shows needle placement (straight arrow) for transpulmonary biopsy of a right paratracheal mass (M). The presence of the superior vena cava (SVC) and azygos vein (curved arrow) precluded anterior or posterior approaches. Note the alveolar hemorrhage in the needle track (arrowheads).
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Complications
Pneumothorax and bleeding are the most common complications of a transpulmonary mediastinal biopsy. Because the needle traverses the lung and two layers of visceral pleura, an increased risk of pneumothorax exists. Placement of the biopsy needle through the lung also creates a risk of alveolar hemorrhage and hemoptysis.
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Conclusions
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This article summarizes the technical aspects, advantages, limitations, and complications of some of the common anatomic approaches used in CT- and US-guided biopsy of mediastinal lesions. Familiarity with cross-sectional mediastinal anatomy facilitates planning of a safe access route for biopsy of deep-seated lesions. Various techniques, such as injection of physiologic saline solution, use of positional maneuvers, and creation of an iatrogenic pneumothorax, help in avoiding puncture of the lung and the visceral pleura, thus decreasing the risk of pneumothorax.
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Acknowledgments
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We thank Ellen M. McDonald, PhD, ELS, for her assistance in editing the manuscript, Nicholas M. Lang for illustrations, Adolfo Chavez III for preparation of images, and Lorena Trachanas for her efforts in preparation of the manuscript.
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Footnotes
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See the commentary by Choplin et al following this article.
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Abstract
Introduction
