DOI: 10.1148/rg.245035209
RadioGraphics 2004;24:1467-1471
© RSNA, 2004
Best Cases from the AFIP
Liver Teratoma1
Lucie C. Martin, MD, FRCPC,
Demetrios Papadatos, MD, FRCPC,
Claudine Michaud, MD, FRCPC and
Jane Thomas, MD, FRCPC
1 From the Departments of Diagnostic Imaging (L.C.M., D.P., C.M.) and Pathology (J.T.), Ottawa Hospital, Ottawa, Ontario, Canada. Received October 21, 2003; revision requested December 16 and received January 28, 2004; accepted April 5. All authors have no financial relationships to disclose. Address correspondence to L.C.M., Department of Radiology, Duke University Medical Center, Box 3808, Durham, NC 27710 (e-mail: luciekilger@hotmail.com).
Index Terms: Liver neoplasms, 761.3199 • Liver neoplasms, diagnosis, 761.3199 • Teratoma, 761.3199
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History
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The patient was a previously healthy 53-year-old woman who presented to a general surgeon in December 2001 after the discovery of an incidental right upper quadrant mass at ultrasound (US). She had initially presented to her family physician several years earlier after multiple episodes of heavy vaginal bleeding and was given the presumptive diagnosis of uterine fibroids. At this time of presentation, the patient was experiencing significant constipation, and it was thought that this could possibly be related to the fibroids causing her extrinsic obstructive bowel symptoms. She underwent barium enema examination for further assessment of her history of constipation and abdominal US for evaluation of the fibroids. At US, an incidental complex mass was noted in the right upper quadrant. She had no symptoms on presentation to the general surgery outpatient clinic. Her constipation had resolved. She had no pain, decreased appetite, weight loss, night sweats, or fever. She was a nonsmoker with an unremarkable medical and surgical history, other than three uncomplicated pregnancies and subsequent tubal ligation. She had no history of trauma and was not currently taking any medications. At physical examination, the abdomen was soft and nontender with no masses or organomegaly detected. Therefore, the patient underwent preoperative computed tomography (CT) and magnetic resonance (MR) imaging of the abdomen.
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Imaging Findings
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Nonenhanced and contrast material–enhanced CT of the abdomen was performed, which demonstrated a lobulated 8.0 x 6.0-cm heterogeneous mass in the posterior right upper quadrant. This mass demonstrated a combination of cystic, fatty, and calcific components on the basis of its various internal attenuations. Only a thin peripheral rim around the mass demonstrated enhancement (Fig 1). On the basis of the imaging characteristics, this lesion was thought to be most in keeping with a teratoma, less likely a liposarcoma, either of retroperitoneal or hepatic origin.
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Figure 1. Contrast-enhanced CT scan of the abdomen shows a well-defined lesion along the posterior right lobe of the liver. The lesion contains a fluid component (1), a fatty component (2), and some calcification (3).
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MR imaging was then performed to further characterize and localize the lesion before surgery. The MR imaging findings confirmed the presence of a heterogeneous mass abutting the bare area of the liver (Fig 2). Superiorly, this mass contained an area that was hypointense on T1-weighted images (Fig 3a) and hyperintense on T2-weighted images (Fig 3b), in keeping with a cystic component. The inferior portion of the mass was more heterogeneous, demonstrating some focal areas of increased signal intensity on the T1-weighted images. These same areas were noted to remain hyperintense on the out-of-phase T1-weighted matching images. This confirms that the hyperintense area on in-phase T1-weighted images represented macroscopic fat (Fig 3c) rather than other types of material that could mimic this appearance, such as blood, microscopic fat, concentrated protein, and melanin. Even with MR imaging and its multiplanar imaging capacity, it was still difficult to ascertain whether this lesion was arising from the retroperitoneum or the liver. The differential diagnosis of this fat-containing mass was unaltered, likely representing a teratoma or less likely a liposarcoma.
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Figure 2. Coronal scout MR image of the abdomen, obtained with true fast imaging with steady-state precession, shows the lesion extending into the bare area of the liver. However, the image does not demonstrate the site of origin of the lesion by means such as a "claw" of tissue surrounding the lesion (the claw sign).
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Figure 3a. (a) Axial out-of-phase T1-weighted MR image shows that the mass has three different signal intensities: marked low signal intensity (1), in keeping with fluid within a cystic component; high signal intensity (2), which represents fatty tissue; and a focus that is relatively isointense to muscle (3), in keeping with a soft-tissue component. (b) Axial fat saturation T2-weighted MR image shows fluid (marked high signal intensity) (1) and the fatty component (2), which has decreased in signal intensity like the adjacent retroperitoneal and subcutaneous macroscopic fat. (c) Axial contrast-enhanced MR image shows minimal peripheral enhancement (arrow), as if there were a capsule.
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Figure 3b. (a) Axial out-of-phase T1-weighted MR image shows that the mass has three different signal intensities: marked low signal intensity (1), in keeping with fluid within a cystic component; high signal intensity (2), which represents fatty tissue; and a focus that is relatively isointense to muscle (3), in keeping with a soft-tissue component. (b) Axial fat saturation T2-weighted MR image shows fluid (marked high signal intensity) (1) and the fatty component (2), which has decreased in signal intensity like the adjacent retroperitoneal and subcutaneous macroscopic fat. (c) Axial contrast-enhanced MR image shows minimal peripheral enhancement (arrow), as if there were a capsule.
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Figure 3c. (a) Axial out-of-phase T1-weighted MR image shows that the mass has three different signal intensities: marked low signal intensity (1), in keeping with fluid within a cystic component; high signal intensity (2), which represents fatty tissue; and a focus that is relatively isointense to muscle (3), in keeping with a soft-tissue component. (b) Axial fat saturation T2-weighted MR image shows fluid (marked high signal intensity) (1) and the fatty component (2), which has decreased in signal intensity like the adjacent retroperitoneal and subcutaneous macroscopic fat. (c) Axial contrast-enhanced MR image shows minimal peripheral enhancement (arrow), as if there were a capsule.
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Pathologic Evaluation
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Approximately 1 month later, the patient underwent surgery. The surgeon could palpate the lesion in the posterior inferior aspect of the right lobe of the liver. Both the kidney and adrenal gland were easily mobilized and therefore not the organ of origin. Once the right hepatic lobe was freed from its peritoneal attachments, it became quite clear visually that the lesion was definitely arising from the right hepatic lobe, even though it could be easily separated from the liver parenchyma at its capsular margin. Only minimal amounts of liver parenchyma had to be resected.
Frozen sectioning by the pathologist revealed that the mass had both a cystic component as well as a mixed solid component, which contained hair and several calcifications.
Further gross pathologic examination revealed the presence of copious amounts of hair and characteristic yellow sebaceous material (Fig 4). At microscopic analysis, this multicystic mass was composed of a wide variety of benign and mature tissues including skin and neural tissues (Fig 5). The final pathologic diagnosis was a benign cystic teratoma.
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Figure 4a. (a) Photograph of the gross pathologic specimen shows a lobulated mass that contains copious amounts of hair and characteristic yellow sebaceous material. (b) Photograph of the cut specimen shows a smooth-walled cavity that contained a sebaceous substance.
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Figure 4b. (a) Photograph of the gross pathologic specimen shows a lobulated mass that contains copious amounts of hair and characteristic yellow sebaceous material. (b) Photograph of the cut specimen shows a smooth-walled cavity that contained a sebaceous substance.
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Figure 5a. Photomicrographs show skin tissue with sebaceous glands and hair follicles (arrow in a), neural tissue (arrow in b), and choroid plexus-like tissue (arrow in c), which confirm the diagnosis of a teratoma.
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Figure 5b. Photomicrographs show skin tissue with sebaceous glands and hair follicles (arrow in a), neural tissue (arrow in b), and choroid plexus-like tissue (arrow in c), which confirm the diagnosis of a teratoma.
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Figure 5c. Photomicrographs show skin tissue with sebaceous glands and hair follicles (arrow in a), neural tissue (arrow in b), and choroid plexus-like tissue (arrow in c), which confirm the diagnosis of a teratoma.
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Discussion
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Teratomas are neoplasms that are composed of tissues not normally found within the organ in which they are located (1). By definition, a teratoma must contain tissue derivatives of at least two or more germ cell layers—namely, ectoderm, mesoderm, and endoderm—and have evidence of organ formation (2). They can be categorized as benign or malignant on the basis of only histologic features and the number of mitotic cells noted. Embryologically, they are thought to arise from primordial germ cells that arrest along their migration path from the allantois hindgut to the gonads during the first weeks of life (3). One theory proposed by Willis is that teratomas arise from foci of totipotent cells in the area of the primitive streak that somehow escape the influence of the primary organizer during embryonic development (4), hence their common midline and paramedial location.
Therefore, these tumors most commonly occur, in order of decreasing frequency, in the ovaries, testes, anterior mediastinum, retroperitoneum, sacrococcygeal region, and cranium (5). Rarely, there have been case reports of these tumors occurring in the gastrointestinal tract and even less commonly in the liver (1). Most liver teratomas are seen in patients under 3 years of age (6), likely reflecting their proposed congenital origin. Most are discovered incidentally, as there is no typical clinical presentation. The symptoms are usually location specific, related to mass effect on adjacent organs. Occasionally, acute symptoms such as pain or even an acute abdomen (7) can develop suddenly, occasionally associated with malignant neoplasms (5), which are thought by some to be related to rapid degeneration (7). For reasons unknown, they more commonly occur in female patients (1) and are most common in the right hepatic lobe (1). Hepatic teratomas are usually well-encapsulated lesions, easily resectable from the surrounding hepatic parenchyma (1), as was noted by our surgeon. Complete resection remains the best treatment option (1), as untreated malignant retroperitoneal teratomas have a mortality rate approaching 100% (5).
As previously described, teratomas must contain at least two of three germ layers, which histologically can include bone, hair, skin, sebum, fat, muscle, neural tissue, and even pancreatic and thyroid tissue in rare instances (8). Plain radiographs can usually demonstrate a soft-tissue mass with secondary mass effects on adjacent organs, as well as calcifications, either rimlike or chunky. Occasionally, a more lucent, fat opacity component can also be appreciated. At US, there may be a hypo- or anechoic component, which represents the cystic portion of this mass. Hyperechoic foci could represent either calcifications or macroscopic fat. These components are differentiated by the abrupt posterior acoustic shadowing behind calcifications but gradual attenuation of the sound beam behind fat. Fat-fluid levels, which occur due to the presence of sebum, are pathognomonic, with the macroscopic fat ranging from hypoechoic to hyperechoic, depending on the differences in acoustic impedance with the adjacent soft tissues (5).
At CT, calcifications and macroscopic fat are readily identified as markedly hyperattenuating and markedly hypoattenuating foci, respectively. The macroscopic fat does not contain any soft-tissue attenuation material within it, nor does it demonstrate any enhancement. A more common differential diagnosis of a fatty retroperitoneal mass is a liposarcoma. However, the presence of a well-defined cystic cavity and chunky calcifications argued against this diagnosis. Very few cases have been imaged with MR imaging. Calcifications are usually inferred by a lack of signal, depending on size, although they can have various signal intensities. Macroscopic fat is typically hyperintense on T1-weighted images and drops in signal intensity after the application of a fat saturation pulse. Cystic components are typically hypointense on T1-weighted images and hyperintense on T2-weighted images, mimicking the signal intensity characteristics of water. Occasionally, a Rokitansky body or dermoid plug, which represents an eccentric protrusion of solid tissue into a cystic component, is noted (2,9). The multiplanar imaging capacity of MR imaging is also very helpful in determining the organ of origin, the extent of the tumor, and the ease of resectability.
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Conclusions
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Teratoma is an uncommonly encountered neoplasm in the liver. However, its unique pathologic features translate into very interesting and pathognomonic imaging features.
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Footnotes
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Editor’s Note.—Everyone who has taken the course in radiologic pathology at the Armed Forces Institute of Pathology (AFIP) remembers bringing beautifully illustrated cases for accession to the Institute. In recent years, the staff of the Department of Radiologic Pathology has judged the "best cases" by organ system, and recognition is given to the winners on the last day of the class. With each issue of RadioGraphics, one or more of these cases are published, written by the winning resident. Radiologic-pathologic correlation is emphasized, and the causes of the imaging signs of various diseases are illustrated.
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References
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- Winter TC, Freeny P. Hepatic teratoma in an adult: case report with a review of the literature. J Clin Gastroenterol 1993; 17:308-310.[Medline]
- Davidson A, Hartman D, Goldman S. Mature teratoma of the retroperitoneum: radiologic, pathologic, and clinical correlation. Radiology 1989; 172:421-425.[Abstract/Free Full Text]
- Col C. Immature teratoma in both mediastinum and liver of a 21-year-old female patient. Acta Med Austriaca 2003; 30:26-28.[CrossRef][Medline]
- Alam K, Maheshwari V, Aziz M, Ghani I. Teratoma of the liver: a case report. Indian J Pathol Microbiol 1998; 41:457-459.[Medline]
- Pakdirat B, Prachaphinyo T, Pakdirat P. Radiology of retroperitoneal cystic teratoma in adult: a case report. J Med Assoc Thai 1994; 77:271-274.[Medline]
- Todani T, Tabuchi K, Watanabe Y, Tsutumi A. True hepatic teratoma with high alpha fetoprotein in serum. J Pediatr Surg 1977; 12:591-592.[CrossRef][Medline]
- Pandya J, Pai M, Muchhala S. Retroperitoneal teratoma presenting as an acute abdomen in an elderly person. Indian J Gastroenterol 2000; 19:89-90.[Medline]
- Watanabe I, Kasai M, Suzuki S. True teratoma of the liver: report of a case and review of the literature. Acta Hepatogastroenterol (Stuttg) 1978; 25:40-44.[Medline]
- Choi B, Chi J, Kim S, Chang K, Han M. MR imaging of retroperitoneal teratoma: correlation with CT and pathology. J Comput Assist Tomogr 1989; 13:1083-1086.[Medline]
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History
Imaging Findings
