(Radiographics. 2002;22:19-33.)
© RSNA, 2002
Focal Asymmetric Densities Seen at Mammography: US and Pathologic Correlation1
Polya Samardar, MD,
Ellen Shaw de Paredes, MD,
Margaret M. Grimes, MD and
John D. Wilson, PhD
1 From the Departments of Radiology (P.S., E.S.d.P., J.D.W.) and Pathology (M.M.G.), Medical College of Virginia of Virginia Commonwealth University, Richmond. Presented as an education exhibit at the 2000 RSNA scientific assembly. Received March 22, 2001; revision requested May 18 and received September 21; accepted September 24. Address correspondence to P.S., 9641 Kingscroft Dr, Glen Allen, VA 23060 (e-mail: psamardar@yahoo.com).
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Abstract
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The American College of Radiology (ACR) Breast Imaging Reporting and Data System (BI-RADS) defines four different types of asymmetric breast findings: asymmetric breast tissue, densities seen in one projection, architectural distortion, and focal asymmetric densities. These lesions are frequently encountered at screening and diagnostic mammography and are significant because they may indicate a neoplasm, especially if an associated palpable mass is present. Once these lesions are detected at standard mammography, supplementary breast imaging with additional mammographic views and ultrasonography (US) can be a key aspect of work-up. The role of US in this setting has not been clearly defined. However, a positive US finding such as a solid mass or an area of focal shadowing increases the level of suspicion for malignancy. A thorough knowledge of the patient’s clinical history, along with a fundamental understanding of the ACR BI-RADS lexicon and the role and limitations of supplementary breast imaging, will allow more accurate interpretation of these potentially perplexing soft-tissue findings.
© RSNA, 2002
Index Terms: Breast, 00.91, 00.92 • Breast, US, 00.1298 • Breast neoplasms, 00.32 • Breast neoplasms, radiography, 00.114, 00.115 • Breast neoplasms, US, 00.1298 • Breast radiography, 00.114, 00.115
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LEARNING OBJECTIVES FOR TEST 2
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After reading this article and taking the test, the reader will be able to:
- Describe the various types of asymmetric breast findings seen at mammography.
- Discuss the various benign and malignant causes of these findings.
- Discuss the role of US in the assessment of focal asymmetric densities seen at mammography.
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Introduction
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Although there is clearly a wide variation in breast size and parenchymal pattern, the breasts are generally symmetric structures with similar density and architecture. However, asymmetric breast tissue is encountered relatively frequently, having been reported to occur on 3% of mammograms (1). Asymmetric breast tissue is usually benign and secondary to variations in normal breast tissue, postoperative change, or hormone replacement therapy. However, an asymmetric area may indicate a developing mass or an underlying cancer. In this article, we present different types of asymmetric breast findings and appropriate imaging work-up. We also discuss and illustrate the imaging and pathologic features of various benign and malignant causes of focal asymmetric densities and distortions.
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Types of Asymmetric Breast Findings
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For more accurate work-up and diagnosis of soft-tissue findings at mammography, the American College of Radiology (ACR) Breast Imaging Reporting and Data System (BI-RADS) lexicon provides definitions for four different types of asymmetric breast findings: (a) asymmetric breast tissue, (b) densities seen in one projection, (c) architectural distortion, and (d) focal asymmetric densities (2).
Asymmetric Breast Tissue
The term asymmetric breast tissue refers to a greater volume or density of breast tissue in one breast than in the corresponding area in the contralateral breast (Fig 1). Although asymmetry is often a normal finding, additional evaluation may sometimes be required (2). Asymmetry may be secondary to removal of tissue or to lack of development or more prominent parenchyma in one breast.
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Figure 1a. Hypoplasia of the left breast secondary to radiation therapy. The patient had undergone irradiation of the left hemithorax as a child. Bilateral mediolateral oblique (a) and craniocaudal (b) mammograms demonstrate asymmetric glandular tissue in the right breast relative to the left.
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Figure 1b. Hypoplasia of the left breast secondary to radiation therapy. The patient had undergone irradiation of the left hemithorax as a child. Bilateral mediolateral oblique (a) and craniocaudal (b) mammograms demonstrate asymmetric glandular tissue in the right breast relative to the left.
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Densities Seen in One Projection
A density that is seen on only one standard mammographic view is referred to as a density seen in one projection (Fig 2). Although this finding may represent benign superimposed fibroglandular tissue, additional imaging may reveal a true lesion. True lesions may appear on only one view because they are either obscured by overlapping dense parenchyma or located posteriorly and thus outside the field of view.
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Figure 2a. Density seen in one projection. (a, b) Right mediolateral oblique (a) and craniocaudal (b) mammograms demonstrate a focal density seen in one projection (arrow in a). The lesion is located superiorly and overlies the axillary tail. (c) On a subsequent ultrasonographic (US) image, the lesion is located medially. US-guided core needle biopsy revealed medullary carcinoma in the upper inner quadrant.
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Figure 2b. Density seen in one projection. (a, b) Right mediolateral oblique (a) and craniocaudal (b) mammograms demonstrate a focal density seen in one projection (arrow in a). The lesion is located superiorly and overlies the axillary tail. (c) On a subsequent ultrasonographic (US) image, the lesion is located medially. US-guided core needle biopsy revealed medullary carcinoma in the upper inner quadrant.
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Figure 2c. Density seen in one projection. (a, b) Right mediolateral oblique (a) and craniocaudal (b) mammograms demonstrate a focal density seen in one projection (arrow in a). The lesion is located superiorly and overlies the axillary tail. (c) On a subsequent ultrasonographic (US) image, the lesion is located medially. US-guided core needle biopsy revealed medullary carcinoma in the upper inner quadrant.
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Architectural Distortion
In architectural distortion, a focal area of breast tissue appears distorted with no definable central mass. Spiculations radiate from a common point, and there is an area of focal retraction and tethering of normal parenchyma (Fig 3). Architectural distortion may be associated with breast cancer because cancer infiltration can disrupt parenchymal architecture before there is evidence of a mass. It may also be seen in areas of prior breast injury or surgery, which tend to improve or remain unchanged over time. Therefore, comparison with previous mammographic findings (if available) is essential. Another benign cause of architectural distortion is radial scar, which is a nontraumatic lesion. Unexplained architectural distortion warrants biopsy (2).
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Figure 3a. Architectural distortion. Left mediolateral (a) and craniocaudal (b) mammograms demonstrate a focal architectural distortion located at the 12 o’clock position (arrow). The distortion has a central area of hyperlucency and a few associated punctate microcalcifications. At pathologic analysis, the lesion was seen to represent a radial scar.
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Figure 3b. Architectural distortion. Left mediolateral (a) and craniocaudal (b) mammograms demonstrate a focal architectural distortion located at the 12 o’clock position (arrow). The distortion has a central area of hyperlucency and a few associated punctate microcalcifications. At pathologic analysis, the lesion was seen to represent a radial scar.
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Focal Asymmetric Densities
By definition, a focal asymmetric density is seen on two mammographic views but cannot be accurately identified as a true mass (Fig 4). Although a focal asymmetric density may represent normal breast tissue, further evaluation is often warranted to exclude a true mass or architectural distortion.
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Figure 4a. Focal asymmetric density. Bilateral mediolateral oblique (a) and left craniocaudal (b) mammograms show a focal asymmetric density in the upper outer quadrant (arrow). This finding had been stable at imaging studies performed over the past 4 years and is consistent with benign fibroglandular tissue.
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Figure 4b. Focal asymmetric density. Bilateral mediolateral oblique (a) and left craniocaudal (b) mammograms show a focal asymmetric density in the upper outer quadrant (arrow). This finding had been stable at imaging studies performed over the past 4 years and is consistent with benign fibroglandular tissue.
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Imaging Work-up of Asymmetric Breast Findings
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Off-angle mammographic views can be helpful in the work-up of asymmetric breast findings. A density seen in one projection requires additional views to determine if it represents superimposed tissue or a true lesion. If the lesion is seen only on the mediolateral oblique view, a straight mediolateral view is obtained to determine if the lesion persists and where it is located (Fig 5). Lesions that move superiorly on the mediolateral view relative to the mediolateral oblique view are located medially, whereas lateral lesions move inferiorly on the mediolateral view. Similarly, if a lesion is seen only on the craniocaudal view, rolled craniocaudal views are obtained to confirm its presence and show its location (3).
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Figure 5a. Invasive lobular carcinoma in a postmenopausal woman. (a) Bilateral craniocaudal screening mammograms show a focal density seen in only one projection laterally in the left breast (arrow). (b, c) On medially (b) and laterally (c) rolled craniocaudal mammograms, the lesion (arrow) persists and rolls with the top of the breast, indicating that it is located superiorly. Stereotactic biopsy (superior approach) demonstrated invasive lobular carcinoma.
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Figure 5b. Invasive lobular carcinoma in a postmenopausal woman. (a) Bilateral craniocaudal screening mammograms show a focal density seen in only one projection laterally in the left breast (arrow). (b, c) On medially (b) and laterally (c) rolled craniocaudal mammograms, the lesion (arrow) persists and rolls with the top of the breast, indicating that it is located superiorly. Stereotactic biopsy (superior approach) demonstrated invasive lobular carcinoma.
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Figure 5c. Invasive lobular carcinoma in a postmenopausal woman. (a) Bilateral craniocaudal screening mammograms show a focal density seen in only one projection laterally in the left breast (arrow). (b, c) On medially (b) and laterally (c) rolled craniocaudal mammograms, the lesion (arrow) persists and rolls with the top of the breast, indicating that it is located superiorly. Stereotactic biopsy (superior approach) demonstrated invasive lobular carcinoma.
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To assess the shape and margins of a potential lesion, a spot compression view is obtained. In cases of architectural distortion, a spot compression view will often more clearly delineate the spiculation. If a density is clearly evident on two views but appears less dense or less prominent on the spot compression view, one should not as-sume that it is not a true lesion: Spot compression displaces the normal tissue away and may make a true lesion appear less dense (Fig 6).
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Figure 6a. Invasive ductal carcinoma. (a, b) Right mediolateral oblique (a) and craniocaudal (b) mammograms show a focal architectural distortion in the upper quadrant (arrow). The lesion is more clearly delineated on the craniocaudal view than on the mediolateral oblique view. (c) On a spot compression mammogram, the distortion appears less dense and less spiculated (arrow); consequently, biopsy was not performed. However, at clinical examination performed 6 months later, the area had become palpable, and subsequent biopsy revealed invasive ductal carcinoma.
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Figure 6b. Invasive ductal carcinoma. (a, b) Right mediolateral oblique (a) and craniocaudal (b) mammograms show a focal architectural distortion in the upper quadrant (arrow). The lesion is more clearly delineated on the craniocaudal view than on the mediolateral oblique view. (c) On a spot compression mammogram, the distortion appears less dense and less spiculated (arrow); consequently, biopsy was not performed. However, at clinical examination performed 6 months later, the area had become palpable, and subsequent biopsy revealed invasive ductal carcinoma.
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Figure 6c. Invasive ductal carcinoma. (a, b) Right mediolateral oblique (a) and craniocaudal (b) mammograms show a focal architectural distortion in the upper quadrant (arrow). The lesion is more clearly delineated on the craniocaudal view than on the mediolateral oblique view. (c) On a spot compression mammogram, the distortion appears less dense and less spiculated (arrow); consequently, biopsy was not performed. However, at clinical examination performed 6 months later, the area had become palpable, and subsequent biopsy revealed invasive ductal carcinoma.
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US can also provide valuable information. The presence of a mass at US, particularly a hypoechoic solid mass or focal shadowing, raises suspi-cion for malignancy and definitely warrants biopsy (Figs 7, 8). US can also demonstrate a cyst within a focal density that might prompt routine follow-up (Fig 9) (4).
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Figure 7a. Invasive lobular carcinoma in a 48-year-old woman who presented with mild thickening in the left upper outer quadrant. (a) Left craniocaudal spot compression mammogram demonstrates slight architectural distortion in the affected region (arrow). (b) US image demonstrates an irregular, hypoechoic solid mass with shadowing, which represents a highly suspicious finding. Clinical examination demonstrated localized thickening but no dominant palpable mass. However, pathologic analysis revealed invasive lobular carcinoma.
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Figure 7b. Invasive lobular carcinoma in a 48-year-old woman who presented with mild thickening in the left upper outer quadrant. (a) Left craniocaudal spot compression mammogram demonstrates slight architectural distortion in the affected region (arrow). (b) US image demonstrates an irregular, hypoechoic solid mass with shadowing, which represents a highly suspicious finding. Clinical examination demonstrated localized thickening but no dominant palpable mass. However, pathologic analysis revealed invasive lobular carcinoma.
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Figure 8a. Invasive ductal cancer in a 45-year-old woman who presented with a palpable mass in the right axilla. (a) Bilateral mediolateral oblique mammograms show an enlarged lymph node in the area corresponding to the mass (arrow). (b) Bilateral craniocaudal mammograms reveal a focal asymmetric density at the 12 o’clock position in the right breast (arrow). Additional mammography and US were performed due to suspected occult malignancy. (c) On a spot compression mammogram, the asymmetric density persists and is isodense relative to surrounding tissue. (d) US image reveals a corresponding hypoechoic solid mass that proved to be invasive ductal cancer at US-guided core needle biopsy.
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Figure 8b. Invasive ductal cancer in a 45-year-old woman who presented with a palpable mass in the right axilla. (a) Bilateral mediolateral oblique mammograms show an enlarged lymph node in the area corresponding to the mass (arrow). (b) Bilateral craniocaudal mammograms reveal a focal asymmetric density at the 12 o’clock position in the right breast (arrow). Additional mammography and US were performed due to suspected occult malignancy. (c) On a spot compression mammogram, the asymmetric density persists and is isodense relative to surrounding tissue. (d) US image reveals a corresponding hypoechoic solid mass that proved to be invasive ductal cancer at US-guided core needle biopsy.
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Figure 8c. Invasive ductal cancer in a 45-year-old woman who presented with a palpable mass in the right axilla. (a) Bilateral mediolateral oblique mammograms show an enlarged lymph node in the area corresponding to the mass (arrow). (b) Bilateral craniocaudal mammograms reveal a focal asymmetric density at the 12 o’clock position in the right breast (arrow). Additional mammography and US were performed due to suspected occult malignancy. (c) On a spot compression mammogram, the asymmetric density persists and is isodense relative to surrounding tissue. (d) US image reveals a corresponding hypoechoic solid mass that proved to be invasive ductal cancer at US-guided core needle biopsy.
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Figure 8d. Invasive ductal cancer in a 45-year-old woman who presented with a palpable mass in the right axilla. (a) Bilateral mediolateral oblique mammograms show an enlarged lymph node in the area corresponding to the mass (arrow). (b) Bilateral craniocaudal mammograms reveal a focal asymmetric density at the 12 o’clock position in the right breast (arrow). Additional mammography and US were performed due to suspected occult malignancy. (c) On a spot compression mammogram, the asymmetric density persists and is isodense relative to surrounding tissue. (d) US image reveals a corresponding hypoechoic solid mass that proved to be invasive ductal cancer at US-guided core needle biopsy.
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Figure 9a. Simple cyst. (a) Right mediolateral mammogram demonstrates a focal density seen in one projection in the superior aspect of the breast (arrow). This lesion was less prominent on earlier mammograms (not shown). (b) US image demonstrates a simple cyst corresponding to the mammographic finding.
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Figure 9b. Simple cyst. (a) Right mediolateral mammogram demonstrates a focal density seen in one projection in the superior aspect of the breast (arrow). This lesion was less prominent on earlier mammograms (not shown). (b) US image demonstrates a simple cyst corresponding to the mammographic finding.
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Developing asymmetric densities need to be evaluated unless they can be explained in terms of benign causes. Patients who undergo estrogen replacement therapy may develop focal as well as diffuse changes at mammography (5,6). If a focal density develops in a patient undergoing hormone replacement therapy, discontinuation of therapy and repeat mammography may demonstrate resolution of the finding (Fig 10). If the density does not resolve, biopsy is indicated. An asymmetric density that becomes less evident but still persists after discontinuation of hormone replacement therapy could hypothetically represent estrogen-sensitive breast cancer.
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Figure 10a. Resolution of a focal density after discontinuation of contraceptive use. (a, b) Left mediolateral oblique mammograms obtained in 1993 (a) and in 1994 after the patient had begun taking oral contraceptives (b) show interval development of a focal asymmetric density (arrow in b). (c) Repeat mammogram obtained 3 weeks after discontinuation of contraceptive use shows resolution of the density. Similar findings may be seen in patients undergoing hormone replacement therapy.
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Figure 10b. Resolution of a focal density after discontinuation of contraceptive use. (a, b) Left mediolateral oblique mammograms obtained in 1993 (a) and in 1994 after the patient had begun taking oral contraceptives (b) show interval development of a focal asymmetric density (arrow in b). (c) Repeat mammogram obtained 3 weeks after discontinuation of contraceptive use shows resolution of the density. Similar findings may be seen in patients undergoing hormone replacement therapy.
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Figure 10c. Resolution of a focal density after discontinuation of contraceptive use. (a, b) Left mediolateral oblique mammograms obtained in 1993 (a) and in 1994 after the patient had begun taking oral contraceptives (b) show interval development of a focal asymmetric density (arrow in b). (c) Repeat mammogram obtained 3 weeks after discontinuation of contraceptive use shows resolution of the density. Similar findings may be seen in patients undergoing hormone replacement therapy.
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Currently, magnetic resonance (MR) imaging does not have a recognized role in the assessment of breast asymmetry. Although this modality is valuable in the preoperative staging of breast cancer, differentiating between scar tissue and carcinoma, and characterizing changes associated with breast prostheses, its role in assessing breast asymmetry remains unclear (7,8).
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Causes of Asymmetric Densities and Distortions
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Benign Causes
Asymmetric densities and architectural distortions of the breast can be difficult to evaluate. Postsurgical scarring is a common benign cause of these lesions. Architectural distortion can persist for years after surgery (Fig 11). Although recurrent tumor is unusual during the first year following lumpectomy, an enlarging area of architectural distortion warrants careful attention and perhaps biopsy.
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Figure 11a. Architectural distortion due to prior biopsy. Left mediolateral oblique (a) and craniocaudal (b) mammograms show a focal architectural distortion (arrow) at the site of a prior biopsy (metallic marker). The distortion is more prominent on the craniocaudal view than on the mediolateral oblique view. This finding is consistent with postsurgical scarring, one of the benign causes of asymmetric densities and distortions.
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Figure 11b. Architectural distortion due to prior biopsy. Left mediolateral oblique (a) and craniocaudal (b) mammograms show a focal architectural distortion (arrow) at the site of a prior biopsy (metallic marker). The distortion is more prominent on the craniocaudal view than on the mediolateral oblique view. This finding is consistent with postsurgical scarring, one of the benign causes of asymmetric densities and distortions.
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Noniatrogenic trauma with associated hematoma or fat necrosis is another benign cause of asymmetry and distortion. Spiculations can be a result of blood tracking along the trabeculae of the breast. Clinical history is often important in the interpretation of mammographic findings in these patients.
A radial scar is seen as a focal area of architectural distortion that often contains a central area of hyperlucency (Fig 12). Associated microcalcifications may also be present. Because radial scar cannot be diagnosed with mammography alone, biopsy is indicated.
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Figure 12a. Radial scar. (a, b) Bilateral craniocaudal (a) and right craniocaudal spot compression (b) mammograms demonstrate a focal area of architectural distortion with spiculation in the medial aspect of the right breast (arrow). The lesion was nonpalpable and was excised following needle localization. (c) Photograph of the gross specimen shows a radial scar as a dense, fibrotic lesion with spiculation. Scale is in centimeters. (d) Photomicrograph (hematoxylin-eosin stain) depicts the radial scar as a proliferative lesion of the breast composed of sclerosing adenosis and fibrosis in a characteristic "wheel spoke" orientation.
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Figure 12b. Radial scar. (a, b) Bilateral craniocaudal (a) and right craniocaudal spot compression (b) mammograms demonstrate a focal area of architectural distortion with spiculation in the medial aspect of the right breast (arrow). The lesion was nonpalpable and was excised following needle localization. (c) Photograph of the gross specimen shows a radial scar as a dense, fibrotic lesion with spiculation. Scale is in centimeters. (d) Photomicrograph (hematoxylin-eosin stain) depicts the radial scar as a proliferative lesion of the breast composed of sclerosing adenosis and fibrosis in a characteristic "wheel spoke" orientation.
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Figure 12c. Radial scar. (a, b) Bilateral craniocaudal (a) and right craniocaudal spot compression (b) mammograms demonstrate a focal area of architectural distortion with spiculation in the medial aspect of the right breast (arrow). The lesion was nonpalpable and was excised following needle localization. (c) Photograph of the gross specimen shows a radial scar as a dense, fibrotic lesion with spiculation. Scale is in centimeters. (d) Photomicrograph (hematoxylin-eosin stain) depicts the radial scar as a proliferative lesion of the breast composed of sclerosing adenosis and fibrosis in a characteristic "wheel spoke" orientation.
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Figure 12d. Radial scar. (a, b) Bilateral craniocaudal (a) and right craniocaudal spot compression (b) mammograms demonstrate a focal area of architectural distortion with spiculation in the medial aspect of the right breast (arrow). The lesion was nonpalpable and was excised following needle localization. (c) Photograph of the gross specimen shows a radial scar as a dense, fibrotic lesion with spiculation. Scale is in centimeters. (d) Photomicrograph (hematoxylin-eosin stain) depicts the radial scar as a proliferative lesion of the breast composed of sclerosing adenosis and fibrosis in a characteristic "wheel spoke" orientation.
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Ectopic breast tissue and simple cysts are other benign causes of asymmetric densities and distortion. US plays a key role in the diagnosis of these entities (Fig 13). Various fibrocystic conditions such as fibrosis or sclerosing adenosis may demonstrate similar mammographic findings.
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Figure 13a. Ectopic breast tissue in a 30-year-old woman in the 32nd week of pregnancy who presented with an enlarging axillary mass. (a) Right axillary spot compression mammogram demonstrates focal asymmetric glandular tissue in the axilla (arrow). (b) US image shows the tissue with prominent lactiferous ducts (arrow). These mammographic and US findings are consistent with accessory or ectopic breast tissue in the axilla. Accessory breast tissue can lie in the lateral aspect of the breast above the nipple line or in the central to medial aspect of the breast below the nipple line. In such cases, US demonstrates normal parenchyma and ducts.
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Figure 13b. Ectopic breast tissue in a 30-year-old woman in the 32nd week of pregnancy who presented with an enlarging axillary mass. (a) Right axillary spot compression mammogram demonstrates focal asymmetric glandular tissue in the axilla (arrow). (b) US image shows the tissue with prominent lactiferous ducts (arrow). These mammographic and US findings are consistent with accessory or ectopic breast tissue in the axilla. Accessory breast tissue can lie in the lateral aspect of the breast above the nipple line or in the central to medial aspect of the breast below the nipple line. In such cases, US demonstrates normal parenchyma and ducts.
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Other benign causes of asymmetric densities include focal fibroglandular tissue stimulated by replacement hormones or oral contraceptives and unusual breast lesions such as diabetic fibrous mastopathy.
Malignant Causes
The mammographic and US appearances of breast cancers vary. The most worrisome finding associated with a focal area of breast asymmetry or architectural distortion is a palpable mass (Fig 14), which usually requires biopsy. In addition, a new or enlarging area of asymmetry or distortion that cannot be explained on a hormonal basis often warrants biopsy (Fig 15).
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Figure 14a. Invasive ductal carcinoma. Bilateral mediolateral oblique (a) and left mediolateral oblique spot compression (b) mammograms demonstrate a focal asymmetric low-density area in the posterosuperior portion of the left breast (arrows) corresponding to an area of palpable thickening found at clinical examination. Pathologic analysis of the lesion revealed invasive ductal carcinoma.
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Figure 14b. Invasive ductal carcinoma. Bilateral mediolateral oblique (a) and left mediolateral oblique spot compression (b) mammograms demonstrate a focal asymmetric low-density area in the posterosuperior portion of the left breast (arrows) corresponding to an area of palpable thickening found at clinical examination. Pathologic analysis of the lesion revealed invasive ductal carcinoma.
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Figure 15a. Comedocarcinoma in a 35-year-old woman. (a) Left mediolateral oblique baseline mammogram obtained in August 1990 demonstrates a focal asymmetric density in the upper outer quadrant (arrow). The area was thought to be most likely benign. (b) On a follow-up mammogram obtained in February 1991, the density appears more prominent (arrow). Biopsy was performed and demonstrated comedocarcinoma.
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Figure 15b. Comedocarcinoma in a 35-year-old woman. (a) Left mediolateral oblique baseline mammogram obtained in August 1990 demonstrates a focal asymmetric density in the upper outer quadrant (arrow). The area was thought to be most likely benign. (b) On a follow-up mammogram obtained in February 1991, the density appears more prominent (arrow). Biopsy was performed and demonstrated comedocarcinoma.
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Invasive ductal carcinoma is the most common type of breast cancer (9). Ductal carcinomas elicit a desmoplastic reaction that produces fibrosis. In such cases, a hard, palpable mass is commonly found at clinical examination. At US, invasive ductal carcinoma typically manifests as an irregular, hypoechoic mass with or without posterior acoustic shadowing (Fig 16).
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Figure 16a. Invasive ductal carcinoma. (a) Bilateral craniocaudal mammograms demonstrate a focal asymmetric density in the left middle outer quadrant superimposed over dense parenchyma (arrow). (b) Craniocaudal spot compression mammogram shows a focal distortion with spiculation (arrow). (c) US image demonstrates a solid mass with shadowing corresponding to the lesion, a finding that is highly suspicious for carcinoma. At pathologic analysis, the lesion proved to be stage II invasive ductal carcinoma.
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Figure 16b. Invasive ductal carcinoma. (a) Bilateral craniocaudal mammograms demonstrate a focal asymmetric density in the left middle outer quadrant superimposed over dense parenchyma (arrow). (b) Craniocaudal spot compression mammogram shows a focal distortion with spiculation (arrow). (c) US image demonstrates a solid mass with shadowing corresponding to the lesion, a finding that is highly suspicious for carcinoma. At pathologic analysis, the lesion proved to be stage II invasive ductal carcinoma.
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Figure 16c. Invasive ductal carcinoma. (a) Bilateral craniocaudal mammograms demonstrate a focal asymmetric density in the left middle outer quadrant superimposed over dense parenchyma (arrow). (b) Craniocaudal spot compression mammogram shows a focal distortion with spiculation (arrow). (c) US image demonstrates a solid mass with shadowing corresponding to the lesion, a finding that is highly suspicious for carcinoma. At pathologic analysis, the lesion proved to be stage II invasive ductal carcinoma.
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The second most common type of breast cancer is invasive lobular carcinoma, which accounts for 5%–10% of all malignant breast tumors (10). Invasive lobular carcinoma is thought to arise from the terminal ductules of a breast lobule and invades the normal breast parenchyma in a single-file pattern (11). Because of this pattern of invasion, the tumor often manifests as a subtle area of distortion or asymmetry (Fig 17). A palpable mass or thickening is often noted at clinical examination; associated microcalcifications are rare.
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Figure 17a. Invasive lobular carcinoma in a patient who presented with hardness of the left breast. Standard mammograms showed diffuse increased density of the left breast with edema. (a, b) Mediolateral oblique (a) and craniocaudal (b) mammograms of the right breast show focal architectural distortion at the 9 o’clock position (arrow). Biopsy revealed invasive lobular carcinoma. (c) Photomicrograph (hematoxylin-eosin stain) shows invasive lobular carcinoma that invades the normal parenchyma in a single-file pattern.
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Figure 17b. Invasive lobular carcinoma in a patient who presented with hardness of the left breast. Standard mammograms showed diffuse increased density of the left breast with edema. (a, b) Mediolateral oblique (a) and craniocaudal (b) mammograms of the right breast show focal architectural distortion at the 9 o’clock position (arrow). Biopsy revealed invasive lobular carcinoma. (c) Photomicrograph (hematoxylin-eosin stain) shows invasive lobular carcinoma that invades the normal parenchyma in a single-file pattern.
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Figure 17c. Invasive lobular carcinoma in a patient who presented with hardness of the left breast. Standard mammograms showed diffuse increased density of the left breast with edema. (a, b) Mediolateral oblique (a) and craniocaudal (b) mammograms of the right breast show focal architectural distortion at the 9 o’clock position (arrow). Biopsy revealed invasive lobular carcinoma. (c) Photomicrograph (hematoxylin-eosin stain) shows invasive lobular carcinoma that invades the normal parenchyma in a single-file pattern.
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Tubular carcinoma is a low-grade, well-differentiated form of ductal breast cancer. Lesions are of ductal origin and are characterized by ductal cells invading normal breast tissue and forming groups in the shape of tubules (12). Although these lesions are occasionally palpable, they more frequently go undetected until mammography is performed (Fig 18). Tubular cancers are slow growing and have the most favorable prognosis of all invasive ductal cancers.
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Figure 18a. Tubular carcinoma. Right mediolateral oblique mammogram obtained in 1992 (a) and right mediolateral oblique spot compression mammogram obtained in 1993 (b) demonstrate focal architectural distortion superiorly (arrow in a). No significant change is seen between the two images. Biopsy was performed due to the morphologic features of the affected area. (c) Photomicrograph (hematoxylin-eosin stain) demonstrates tubular carcinoma.
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Figure 18b. Tubular carcinoma. Right mediolateral oblique mammogram obtained in 1992 (a) and right mediolateral oblique spot compression mammogram obtained in 1993 (b) demonstrate focal architectural distortion superiorly (arrow in a). No significant change is seen between the two images. Biopsy was performed due to the morphologic features of the affected area. (c) Photomicrograph (hematoxylin-eosin stain) demonstrates tubular carcinoma.
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Figure 18c. Tubular carcinoma. Right mediolateral oblique mammogram obtained in 1992 (a) and right mediolateral oblique spot compression mammogram obtained in 1993 (b) demonstrate focal architectural distortion superiorly (arrow in a). No significant change is seen between the two images. Biopsy was performed due to the morphologic features of the affected area. (c) Photomicrograph (hematoxylin-eosin stain) demonstrates tubular carcinoma.
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Primary lymphoma of the breast is rare and can have variable mammographic appearances. Although lymphoma usually manifests as an indistinct density, it can also manifest as a circumscribed mass (Fig 19).
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Figure 19a. Primary lymphoma. Right craniocaudal (a) and mediolateral (b) mammograms demonstrate two focal areas of asymmetric density (arrows) in an otherwise fat-replaced breast. At biopsy, both lesions were seen to represent primary lymphoma.
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Figure 19b. Primary lymphoma. Right craniocaudal (a) and mediolateral (b) mammograms demonstrate two focal areas of asymmetric density (arrows) in an otherwise fat-replaced breast. At biopsy, both lesions were seen to represent primary lymphoma.
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Conclusions
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Asymmetric breast tissue, densities seen in one projection, architectural distortion, and focal asymmetric densities are frequently encountered at screening and diagnostic mammography. These findings are significant because they may indicate a neoplasm, especially if an associated palpable mass is present. Once these lesions are detected at standard mammography, supplementary breast imaging with additional mammographic views and US can be a key aspect of work-up. A thorough knowledge of the patient’s clinical history, along with a fundamental understanding of the BI-RADS lexicon and the role and limitations of supplementary breast imaging, will allow more accurate interpretation of these potentially perplexing soft-tissue findings.
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Footnotes
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Abbreviations: ACR = American College of Radiology,
BI-RADS = Breast Imaging Reporting and Data System
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References
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Abstract
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