DOI: 10.1148/rg.226025033
(Radiographics. 2002;22:1305-1325.)
© RSNA, 2002
CT and MR Imaging of Ovarian Tumors with Emphasis on Differential Diagnosis1
Seung Eun Jung, MD,
Jae Mun Lee, MD,
Sung Eun Rha, MD,
Jae Young Byun, MD,
Jung Im Jung, MD and
Seong Tai Hahn, MD
1 From the Department of Radiology, St Mary’s Hospital, Catholic University of Korea, 62 Yeouido-dong, Youngdungpo-gu, Seoul 150-713, Korea (S.E.J., J.M.L., J.I.J., S.T.H.); and the Department of Radiology, Kangnam St Mary’s Hospital, Catholic University of Korea, Seoul (S.E.R., J.Y.B.). Recipient of a Certificate of Merit award for an education exhibit at the 2001 RSNA scientific assembly. Received February 20, 2002; revision requested March 19 and received May 8; accepted May 9. Address correspondence to J.M.L. (e-mail: sejung@catholic.ac.kr).
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Abstract
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Ovarian tumors are classified on the basis of tumor origin as epithelial tumors (serous and mucinous tumors, endometrioid and clear cell carcinomas, Brenner tumor), germ cell tumors (mature and immature teratomas, dysgerminoma, endodermal sinus tumor, embryonal carcinoma), sex cord–stromal tumors (fibrothecoma; granulosa cell, sclerosing stromal, and Sertoli-Leydig cell tumors), and metastatic tumors. Epithelial tumors are primarily cystic and, when malignant, are associated with varying proportions of a solid component. Papillary projections are a distinctive feature of epithelial tumors. Profuse papillary projections are highly suggestive of borderline (low-malignant-potential) or malignant tumor. Ovarian teratomas demonstrate lipid material at computed tomography and magnetic resonance (MR) imaging. Malignant germ cell tumors manifest as a large, complex abdominal mass that contains both solid and cystic components. Tumor markers are helpful in diagnosis. The radiologic appearance of sex cord–stromal tumors varies from small solid masses to large multicystic masses. Granulosa cell tumors are usually large multicystic masses with solid components. Fibrothecoma, sclerosing stromal tumor, and Sertoli-Leydig cell tumors are usually solid masses. Fibromas have very low signal intensity on T2-weighted MR images. Certain radiologic findings predominate for each type of tumor. Knowledge of these key features of ovarian tumors provides the criteria for making a specific diagnosis or substantially narrowing the differential diagnosis.
© RSNA, 2002
Index Terms: Ovary, CT, 852.1211 • Ovary, MR, 852.1214 • Ovary, neoplasms, 852.31, 852.32, 852.33
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LEARNING OBJECTIVES FOR TEST 1
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After reading this article and taking the test, the reader will be able to:
- Describe typical and atypical CT and MR imaging findings in ovarian tumors.
- Identify the specific imaging features of various ovarian tumors.
- Discuss the key features that are helpful in developing a differential diagnosis for these tumors.
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Introduction
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Ovarian tumors are classified as epithelial tumors, germ cell tumors, sex cord–stromal cell tumors, and metastatic tumors on the basis of tumor origin (Table 1) (1). Although ovarian tumors have similar clinical and radiologic features, predominant or specific imaging features may be present in some types of ovarian tumors. Characterization of an ovarian mass is of the utmost importance in the preoperative evaluation of an ovarian neoplasm. It enables the surgeon to anticipate carcinoma of the ovary before the operation so that adequate procedures can be planned (2). In recent years, surgical laparoscopy has been used to manage benign adnexal masses with minimal surgical morbidity (3). Therefore, familiarity with the clinical and imaging features of various ovarian tumors is important in determining the likelihood of a tumor being benign or malignant. In this article, we review the imaging, pathologic, and clinical features of ovarian tumors with emphasis on the computed tomographic (CT) and magnetic resonance (MR) imaging features that indicate a specific diagnosis or allow substantial narrowing of the differential diagnosis.
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Epithelial Tumors
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Epithelial ovarian tumors represent 60% of all ovarian neoplasms and 85% of malignant ovarian neoplasms (1,4). Epithelial tumors are rare in prepubescent patients; their prevalence increases with age and peaks in the sixth and seventh decades of life (1). Subtypes of epithelial tumors include serous, mucinous, endometrioid, clear cell, and Brenner tumors (1,4,5). Epithelial ovarian tumors can be classified as benign (60% of cases), malignant (35%), or borderline (low-malignant-potential) (5%) depending on their histologic characteristics and clinical behavior (6).
Serous versus Mucinous Tumors
Epithelial tumors are typically primarily cystic, may be either unilocular or multilocular, and, when malignant, are associated with varying proportions of solid tissue (6). The two most common types of epithelial neoplasms are serous and mucinous tumors (7). In terms of their pathologic features, disease course, and prognosis, serous and mucinous ovarian tumors are different, but clinical differentiation is not easy (6). In many instances, epithelial tumors tend to be cystic and solid at gross morphologic examination, and their cell types cannot be differentiated on the basis of their appearance at MR imaging, CT, or ultrasonography (US) (6–8). However, some features can aid in differentiating mucinous from serous tumors (Table 2) (6–10). A tumor that manifests as a unilocular or multilocular cystic mass with homogeneous CT attenuation or MR imaging signal intensity of the locules, a thin regular wall or septum, and no endocystic or exocystic vegetation is considered to be a benign serous cystadenoma (Fig 1). A tumor that manifests as a multilocular cystic mass that has a thin regular wall and septa or that contains liquids of different attenuation or signal intensity but has no endocystic or exocystic vegetation is considered to be a benign mucinous cystadenoma (Fig 2). Mucinous cystadenomas tend to be larger than serous cystadenomas at presentation (6–10). About 60% of all the serous ovarian neoplasms are smooth-walled benign cystadenomas, 15% are of low malignant potential, and 25% are malignant. In contrast, 80% of all mucinous ovarian neoplasms are smooth-walled benign cystadenomas, 10%–15% are of low malignant potential, and 5%– 10% are malignant (9–12). Psammoma bodies (calcifications) are seen at histologic analysis in up to 30% of malignant serous tumors (6). Bilaterality and peritoneal carcinomatosis are seen more frequently in serous than in mucinous cystadenocarcinomas (Figs 3, 4) (9). Mucinous adenocarcinoma can rupture and is associated with pseudomyxoma peritonei (Fig 5) (10).
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Figure 1. Benign serous cystadenoma in a 49-year-old woman. Contrast material-enhanced CT scan shows a unilocular cystic mass in the right lower quadrant (arrows). The wall of the mass is not delineated, and there is no evidence of any excrescence within it.
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Figure 2. Benign mucinous cystadenoma in a 26-year-old woman. Contrast-enhanced CT scan shows a large, multilocular cystic mass (arrows) with a smooth contour, honeycomb appearance, and heterogeneous attenuation in the locules.
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Figure 3a. Serous cystadenocarcinoma of the ovary with peritoneal carcinomatosis in a 60-year-old woman. Contrast-enhanced CT scans obtained at the level of the liver (a) and upper pole of the kidney (b) show a subcapsular hepatic implant with a scalloped margin (arrows in a). Diffuse multilocular cystic implants are seen along the greater omentum, parietal peritoneum, gastrosplenic ligament, and lesser sac (arrowheads), and calcified peritoneal implants are noted in the gastrosplenic ligaments (arrows in b). Massive ascites is also present.
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Figure 3b. Serous cystadenocarcinoma of the ovary with peritoneal carcinomatosis in a 60-year-old woman. Contrast-enhanced CT scans obtained at the level of the liver (a) and upper pole of the kidney (b) show a subcapsular hepatic implant with a scalloped margin (arrows in a). Diffuse multilocular cystic implants are seen along the greater omentum, parietal peritoneum, gastrosplenic ligament, and lesser sac (arrowheads), and calcified peritoneal implants are noted in the gastrosplenic ligaments (arrows in b). Massive ascites is also present.
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Figure 5a. Ruptured mucinous cystadenocarcinoma in a 36-year-old woman. (a) Sagittal turbo spin-echo T1-weighted MR image (repetition time msec/echo time msec = 464/14) shows a large, multilocular mass with heterogeneous high signal intensity but with variable signal intensity in the locules. (b) On an axial turbo spin-echo T2-weighted MR image (4,511/132), the mass demonstrates high signal intensity, and there are multiple locules with a honeycomb appearance. The tumor wall is disrupted by spillage of the mucinous material (arrows). (c) Gadolinium-enhanced fat-suppressed turbo spin-echo T1-weighted MR image (782/14) demonstrates marked enhancement of the tumor wall and septa.
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Figure 5b. Ruptured mucinous cystadenocarcinoma in a 36-year-old woman. (a) Sagittal turbo spin-echo T1-weighted MR image (repetition time msec/echo time msec = 464/14) shows a large, multilocular mass with heterogeneous high signal intensity but with variable signal intensity in the locules. (b) On an axial turbo spin-echo T2-weighted MR image (4,511/132), the mass demonstrates high signal intensity, and there are multiple locules with a honeycomb appearance. The tumor wall is disrupted by spillage of the mucinous material (arrows). (c) Gadolinium-enhanced fat-suppressed turbo spin-echo T1-weighted MR image (782/14) demonstrates marked enhancement of the tumor wall and septa.
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Figure 5c. Ruptured mucinous cystadenocarcinoma in a 36-year-old woman. (a) Sagittal turbo spin-echo T1-weighted MR image (repetition time msec/echo time msec = 464/14) shows a large, multilocular mass with heterogeneous high signal intensity but with variable signal intensity in the locules. (b) On an axial turbo spin-echo T2-weighted MR image (4,511/132), the mass demonstrates high signal intensity, and there are multiple locules with a honeycomb appearance. The tumor wall is disrupted by spillage of the mucinous material (arrows). (c) Gadolinium-enhanced fat-suppressed turbo spin-echo T1-weighted MR image (782/14) demonstrates marked enhancement of the tumor wall and septa.
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Benign versus Low-Malignant-Potential and Malignant Tumors
Benign serous and mucinous tumors are common, but benign endometrioid tumors are very rare, and all clear cell carcinomas are malignant (6). The imaging features that are more suggestive of either benignity or malignancy are summarized in Table 3 (6–13).
Features that are more suggestive of benign epithelial tumors include a diameter less than 4 cm, entirely cystic components, a wall thickness less than 3 mm, lack of internal structure, and the absence of both ascites and invasive characteristics such as peritoneal disease or adenopathy (10). Exceptionally large benign neoplasms occur are occasionally seen and are more likely to remain clinically silent as they grow (11). Epithelial tumors with low malignant potential demonstrate more proliferation of papillary projections than do benign cystadenomas (Fig 6) and are often seen in younger patients (14,15). Epithelial tumors with low malignant potential have a much better prognosis than do ovarian carcinomas. They offer the potential for ovarian-uterine–sparing surgery and have less frequent indications for adjuvant chemotherapy; however, like carcinomas, they require initial staging surgery (16,17).
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Figure 6. Borderline mucinous tumor in a 20-year-old woman. Contrast-enhanced CT scan shows a large, multilocular cystic mass with variable attenuation in the locules and enhancing solid-tissue elements (arrows).
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Papillary projections are characteristic features of some epithelial neoplasms of the ovary. Histologically, papillary projections represent folds of the proliferating neoplasmic epithelium growing over a stromal core. T2-weighted MR images demonstrate the structure of a hypointense fibrous core that supports the hyperintense edematous stroma (Fig 7) (7,16). Identification of papillary projections on an imaging study is important because they are the single best predictors of an epithelial neoplasm and may correlate with the aggressiveness of the tumor. Papillary projections are usually absent in benign cystadenomas; if they are present, they are generally small. Papillary projections are profuse in epithelial tumors with low malignant potential and are often present in invasive carcinomas, but the gross appearance of the tumor is dominated by a solid component. A previous CT and MR imaging study found papillary projections in 13% of benign neoplasms, 67% of low-malignant-potential neoplasms, and 38% of malignant neoplasms (16).
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Figure 7a. Papillary serous cystadenocarcinoma in a 53-year-old woman. (a) Axial turbo spin-echo T2-weighted MR image (3,650/99) shows a multilocular mass (solid arrows) around the uterus (U) with irregular solid components (open arrows) and intracystic papillary projections (arrowheads). The mass consists of a low-signal-intensity fibrous core and barely visible edematous stroma. (b) On an axial inversion-recovery MR image (4,890/60), a high-signal-intensity edematous stroma of papillary projections (arrowheads) is clearly seen, whereas the solid component (arrows) has low signal intensity. (c) Sagittal gadolinium-enhanced fat-suppressed turbo spin-echo T1-weighted MR image (905/12) shows marked enhancement of the papillary projections (arrowheads) and solid component (arrow) but less enhancement of the fibrous components.
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Figure 7b. Papillary serous cystadenocarcinoma in a 53-year-old woman. (a) Axial turbo spin-echo T2-weighted MR image (3,650/99) shows a multilocular mass (solid arrows) around the uterus (U) with irregular solid components (open arrows) and intracystic papillary projections (arrowheads). The mass consists of a low-signal-intensity fibrous core and barely visible edematous stroma. (b) On an axial inversion-recovery MR image (4,890/60), a high-signal-intensity edematous stroma of papillary projections (arrowheads) is clearly seen, whereas the solid component (arrows) has low signal intensity. (c) Sagittal gadolinium-enhanced fat-suppressed turbo spin-echo T1-weighted MR image (905/12) shows marked enhancement of the papillary projections (arrowheads) and solid component (arrow) but less enhancement of the fibrous components.
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Figure 7c. Papillary serous cystadenocarcinoma in a 53-year-old woman. (a) Axial turbo spin-echo T2-weighted MR image (3,650/99) shows a multilocular mass (solid arrows) around the uterus (U) with irregular solid components (open arrows) and intracystic papillary projections (arrowheads). The mass consists of a low-signal-intensity fibrous core and barely visible edematous stroma. (b) On an axial inversion-recovery MR image (4,890/60), a high-signal-intensity edematous stroma of papillary projections (arrowheads) is clearly seen, whereas the solid component (arrows) has low signal intensity. (c) Sagittal gadolinium-enhanced fat-suppressed turbo spin-echo T1-weighted MR image (905/12) shows marked enhancement of the papillary projections (arrowheads) and solid component (arrow) but less enhancement of the fibrous components.
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Imaging findings that are suggestive of malignant tumors include a thick, irregular wall; thick septa; papillary projections; and a large soft-tissue component with necrosis (10). Ancillary findings of pelvic organ invasion, implants (peritoneal, omental, mesenteric), ascites, and adenopathy increase diagnostic confidence for malignancy (Fig 3) (7). Features such as wall thickening, septa, and multilocularity are less reliable indicators of malignancy because they are frequently seen in benign neoplasms, particularly cystadenofibromas, mucinous cystadenomas, and endometriomas (17).
Endometrioid Carcinoma
Endometrioid carcinomas represent approximately 10%–15% of all ovarian carcinomas. They are almost always malignant. About 15%–30% are associated with synchronous endometrial carcinoma or endometrial hyperplasia (11,12). Although rare, endometrioid carcinoma is the most common malignant neoplasm arising from endometriosis, followed by clear cell carcinoma (18,19). Bilateral involvement is seen in 30%–50% of cases (11,12). Imaging findings are nonspecific and include a large, complex cystic mass with solid components. Endometrial thickening can also be seen on imaging studies (Fig 8) (6).
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Figure 8a. Endometrioid carcinoma of the ovary and endometrial carcinoma of the uterus in a 38-year-old woman. (a) Contrast-enhanced lower abdominal CT scan shows a complex cystic and solid tumor with enhancement of the solid-tissue elements and a thick, irregular wall. (b) Contrast-enhanced pelvic CT scan shows a widened endometrial cavity with a nodular enhancing solid mass (arrowheads).
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Figure 8b. Endometrioid carcinoma of the ovary and endometrial carcinoma of the uterus in a 38-year-old woman. (a) Contrast-enhanced lower abdominal CT scan shows a complex cystic and solid tumor with enhancement of the solid-tissue elements and a thick, irregular wall. (b) Contrast-enhanced pelvic CT scan shows a widened endometrial cavity with a nodular enhancing solid mass (arrowheads).
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Clear Cell Carcinoma
Clear cell carcinomas represent approximately 5% of ovarian carcinomas and are always malignant (12). The majority (75%) of clear cell carcinomas are stage I disease whose prognosis appears to be better than that of other ovarian cancers (20,21). Clear cell carcinoma may develop in patients with endometriosis who develop ovarian cancer. A large endometrioma with solid components suggests malignancy and must be removed (11,12). Common imaging findings in clear cell carcinoma include a unilocular or large cyst with solid protrusions (Fig 9). The cyst margin is almost always smooth, and its signal intensity on T1-weighted MR images varies from low to very high. The solid protrusions are often both round and few in number (21). These findings suggest, but are not specific for, malignant tumor. Although these findings most likely indicate a serous tumor with low malignant potential or a serous cystadenocarcinoma, the differential diagnosis should include clear cell carcinoma.
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Figure 9a. Clear cell carcinoma in a 42-year-old woman. (a) Sagittal turbo spin-echo T2-weighted MR image (4,275/138) demonstrates a large cystic mass (M) with hypointense, irregular solid protrusions peripherally. U = uterus. (b) Gadolinium-enhanced fat-suppressed fast low-angle shot (FLASH) T1-weighted MR image (147/4.8) demonstrates marked enhancement of the solid portions of the mass.
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Figure 9b. Clear cell carcinoma in a 42-year-old woman. (a) Sagittal turbo spin-echo T2-weighted MR image (4,275/138) demonstrates a large cystic mass (M) with hypointense, irregular solid protrusions peripherally. U = uterus. (b) Gadolinium-enhanced fat-suppressed fast low-angle shot (FLASH) T1-weighted MR image (147/4.8) demonstrates marked enhancement of the solid portions of the mass.
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Brenner Tumor
Brenner tumors are composed of transitional cells with dense stroma. They represent about 2%–3% of ovarian tumors and are rarely malignant. Brenner tumors are usually small (<2 cm) and discovered incidentally, but affected patients may present with a palpable mass or pain. Brenner tumors are associated with other ovarian tumors in 30% of cases (8,22,23).
Brenner tumors manifest as a multilocular cystic mass with a solid component or as a small, mostly solid mass (Fig 10). At CT, the solid components of these masses are mildly or moderately enhanced. At T2-weighted MR imaging, the dense fibrous stroma demonstrates lower signal intensity similar to that of a fibroma. Extensive amorphous calcification is often present within the solid component (22,23).
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Figure 10. Incidentally discovered Brenner tumor in a 68-year-old woman. Contrast-enhanced CT scan shows a small, ovoid solid mass with homogeneous enhancement (arrows), a finding that is nonspecific for a solid tumor.
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Germ Cell Tumors
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Tumors of germ cell origin are the second most common group of ovarian neoplasms, representing 15%–20% of all ovarian tumors. This group of tumors includes mature teratoma, immature teratoma, dysgerminoma, endodermal sinus tumor, embryonal carcinoma, and choriocarcinoma (9,24). Of all the germ cell tumors, only mature teratoma is benign; however, it is by far the most common lesion in this group. All the other tumors are malignant and account for less than 5% of malignant ovarian tumors. Malignant germ cell tumors are generally large and nonspecific with a complex but predominantly solid imaging appearance. Elevated levels of serum 
-fetoprotein and human chorionic gonadotropin (HCG) can also help establish the diagnosis (24–26).
Mature Teratoma
Mature teratoma is the most common benign ovarian tumor in women less than 45 years old. These teratomas are composed of mature tissue from two or more embryonic germ cell layers. At gross pathologic examination, mature cystic teratomas are unilocular, and in 88% of cases, they are filled with sebaceous material and lined by squamous epithelium (25). Hair follicles, skin glands, muscle, and other tissues lie within the wall. There is usually a raised protuberance projecting into the cyst cavity known as the Rokitansky nodule. Most of the hair typically arises from this protuberance. When bone or teeth are present, they tend to be located within this nodule (25,26).
At any imaging modality, mature teratomas demonstrate a broad spectrum of findings, ranging from purely cystic (Fig 11), to a mixed mass with all the components of the three germ cell layers (Figs 12, 13), to a noncystic mass composed predominantly of fat (Fig 14).
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Figure 11. Atypical mature teratoma with a purely cystic component in a 16-year-old girl. Contrast-enhanced CT scan shows a large cystic mass with multiple septa, one of which contains calcifications (arrows). There is no evidence of a fatty component.
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Figure 12a. Mature teratoma in a 22-year-old woman. (a) Axial US image demonstrates a mostly echogenic mass (arrows) with areas of sound attenuation. (b) Contrast-enhanced CT scan shows a cystic tumor with fat and calcification (arrows).
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Figure 12b. Mature teratoma in a 22-year-old woman. (a) Axial US image demonstrates a mostly echogenic mass (arrows) with areas of sound attenuation. (b) Contrast-enhanced CT scan shows a cystic tumor with fat and calcification (arrows).
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Figure 13a. Mature teratoma in a 21-year-old woman. (a) Conventional radiograph shows a large mass with fat opacity and multiple toothlike calcifications, findings that indicate a typical mature teratoma. (b) Axial turbo spin-echo T1-weighted MR image (800/12) shows a well-defined round, hyperintense mass with hypointense calcifications and a mural nodule (arrows). (c) On a sagittal turbo spin-echo T2-weighted MR image (3,800/99), the tumor is isointense relative to subcutaneous fat. The calcifications have low signal intensity (arrows), whereas the Rokitansky protuberance has high signal intensity (arrowheads). (d) Gadolinium-enhanced fat-suppressed FLASH T1-weighted MR image (147/4.8) demonstrates the mass with markedly decreased signal intensity compared with the non-fat-suppressed T1-weighted image (cf b).
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Figure 13b. Mature teratoma in a 21-year-old woman. (a) Conventional radiograph shows a large mass with fat opacity and multiple toothlike calcifications, findings that indicate a typical mature teratoma. (b) Axial turbo spin-echo T1-weighted MR image (800/12) shows a well-defined round, hyperintense mass with hypointense calcifications and a mural nodule (arrows). (c) On a sagittal turbo spin-echo T2-weighted MR image (3,800/99), the tumor is isointense relative to subcutaneous fat. The calcifications have low signal intensity (arrows), whereas the Rokitansky protuberance has high signal intensity (arrowheads). (d) Gadolinium-enhanced fat-suppressed FLASH T1-weighted MR image (147/4.8) demonstrates the mass with markedly decreased signal intensity compared with the non-fat-suppressed T1-weighted image (cf b).
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Figure 13c. Mature teratoma in a 21-year-old woman. (a) Conventional radiograph shows a large mass with fat opacity and multiple toothlike calcifications, findings that indicate a typical mature teratoma. (b) Axial turbo spin-echo T1-weighted MR image (800/12) shows a well-defined round, hyperintense mass with hypointense calcifications and a mural nodule (arrows). (c) On a sagittal turbo spin-echo T2-weighted MR image (3,800/99), the tumor is isointense relative to subcutaneous fat. The calcifications have low signal intensity (arrows), whereas the Rokitansky protuberance has high signal intensity (arrowheads). (d) Gadolinium-enhanced fat-suppressed FLASH T1-weighted MR image (147/4.8) demonstrates the mass with markedly decreased signal intensity compared with the non-fat-suppressed T1-weighted image (cf b).
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Figure 13d. Mature teratoma in a 21-year-old woman. (a) Conventional radiograph shows a large mass with fat opacity and multiple toothlike calcifications, findings that indicate a typical mature teratoma. (b) Axial turbo spin-echo T1-weighted MR image (800/12) shows a well-defined round, hyperintense mass with hypointense calcifications and a mural nodule (arrows). (c) On a sagittal turbo spin-echo T2-weighted MR image (3,800/99), the tumor is isointense relative to subcutaneous fat. The calcifications have low signal intensity (arrows), whereas the Rokitansky protuberance has high signal intensity (arrowheads). (d) Gadolinium-enhanced fat-suppressed FLASH T1-weighted MR image (147/4.8) demonstrates the mass with markedly decreased signal intensity compared with the non-fat-suppressed T1-weighted image (cf b).
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Figure 14. Mature teratoma with a mainly fatty component in a 36-year-old woman. Contrast-enhanced CT scan shows a large, fatty mass in the pelvic cavity (arrows). Mature teratomas demonstrate a wide spectrum of imaging findings because they are composed of three germ cell layers.
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US findings in mature cystic teratomas vary from a cystic lesion with a densely echogenic tubercle (Rokitansky nodule) projecting into the cyst lumen, to a diffusely or partially echogenic mass with the echogenic area usually demonstrating sound attenuation owing to sebaceous material and hair within the cyst cavity (Fig 12), to multiple thin, echogenic bands caused by hair in the cyst cavity (26–28). The dermoid plug is echogenic, with shadowing due to adipose tissue or calcifications within the plug or to hair arising from it (26). At CT, fat attenuation within a cyst, with or without calcification in the wall, is diagnostic for mature cystic teratoma (Fig 12b) (29, 30). At MR imaging, the sebaceous component of dermoid cysts has very high signal intensity on T1-weighted images similar to that of retroperitoneal fat. The signal intensity of the sebaceous component on T2-weighted images is variable, usually near that of fat (Fig 13c) (26,30).
Mature cystic teratoma may be associated with complications from torsion, rupture, or malignant degeneration (26,31). The tumors can rupture, causing leakage of the liquefied sebaceous contents into the peritoneum and resulting in granulomatous peritonitis (26). Less common forms of mature teratomas are the monodermal types, which include struma ovarii (in which mature thyroid tissue predominates) and carcinoids (26).
Immature Teratoma
Immature teratoma represents less than 1% of all teratomas and contains immature tissue from all three germ cell layers (24,26). The tumor strikes during the first 2 decades of life. Benign mature teratomas must be differentiated from malignant, immature teratomas, which have prominent solid components and may demonstrate internal necrosis or hemorrhage. Mature tissue elements similar to those seen in mature cystic teratoma are invariably present (Fig 15) (24,26). Radiologic examination reveals a large, complex mass with cystic and solid components and scattered calcifications; in contrast, calcification in mature teratomas is localized to mural nodules (24). Small foci of fat are also seen in immature teratomas. These tumors grow rapidly and frequently demonstrate perforation of the capsule. The tumor capsule is not always well defined (Fig 16) (26).
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Figure 15a. Immature teratoma in a 23-year-old woman. (a) Contrast-enhanced pelvic CT scan shows a large mass with a large soft-tissue component, a cystic portion, small foci of fat, and scattered calcifications. (b) CT scan obtained at the level of the renal hilum demonstrates extensive retroperitoneal adenopathy.
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Figure 15b. Immature teratoma in a 23-year-old woman. (a) Contrast-enhanced pelvic CT scan shows a large mass with a large soft-tissue component, a cystic portion, small foci of fat, and scattered calcifications. (b) CT scan obtained at the level of the renal hilum demonstrates extensive retroperitoneal adenopathy.
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Figure 16a. Ruptured immature teratoma in a 19-year-old woman. Contrast-enhanced CT scans obtained at the level of the renal hilum (a) and midabdomen (b) show a large, heterogeneous mass with scattered calcifications (solid arrows) and foci of fat (open arrows in b). Perforation of the capsule (arrowheads in a) and tumor in the peritoneum are both present.
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Figure 16b. Ruptured immature teratoma in a 19-year-old woman. Contrast-enhanced CT scans obtained at the level of the renal hilum (a) and midabdomen (b) show a large, heterogeneous mass with scattered calcifications (solid arrows) and foci of fat (open arrows in b). Perforation of the capsule (arrowheads in a) and tumor in the peritoneum are both present.
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Dysgerminoma
Dysgerminomas are rare ovarian tumors that occur predominantly in young women. This tumor is the ovarian counterpart of seminoma of the testis (24). Dysgerminoma in its pure form is not associated with endocrine hormone secretion. However, syncytiotrophoblastic giant cells, which produce HCG, are present in 5% of dysgerminomas and can cause elevation of serum HCG levels. Calcification may be present in a speckled pattern (32). Characteristic imaging findings include multilobulated solid masses with prominent fibrovascular septa (Fig 17). The anechoic, low-signal-intensity, or low-attenuation area of the tumor represents necrosis and hemorrhage (Fig 18) (32,33).
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Figure 17. Dysgerminoma in an 18-year-old woman. Contrast-enhanced CT scan shows a large, multilobulated solid mass with highly enhancing fibrovascular septa (arrows) and cystic change (arrowheads).
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Figure 18a. Dysgerminoma in a 17-year-old girl. (a) Axial turbo spin-echo T2-weighted MR image (3,800/99) shows a large, multilobulated mass with intermediate signal intensity and persistent low signal intensity of the septa (arrows). The irregular high-signal-intensity areas (arrowheads) indicate necrosis. (b) Axial gadolinium-enhanced turbo spin-echo T1-weighted MR image (782/14) demonstrates relatively homogeneous enhancement with persistent low signal intensity of the septa (arrows) and unenhanced necrotic areas (arrowheads).
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Figure 18b. Dysgerminoma in a 17-year-old girl. (a) Axial turbo spin-echo T2-weighted MR image (3,800/99) shows a large, multilobulated mass with intermediate signal intensity and persistent low signal intensity of the septa (arrows). The irregular high-signal-intensity areas (arrowheads) indicate necrosis. (b) Axial gadolinium-enhanced turbo spin-echo T1-weighted MR image (782/14) demonstrates relatively homogeneous enhancement with persistent low signal intensity of the septa (arrows) and unenhanced necrotic areas (arrowheads).
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Endodermal Sinus Tumor
Endodermal sinus tumor, also known as yolk sac tumor, is a rare malignant ovarian tumor that usually occurs in the second decade of life (24). The tumor manifests as a large, complex pelvic mass that extends into the abdomen and contains both solid and cystic components (Fig 19). The cystic areas are composed of epithelial line cysts produced by the tumor or of coexisting mature teratomas. These tumors grow rapidly and have a poor prognosis. Affected patients have an elevated serum -fetoprotein level (34,35).
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Figure 19. Endodermal sinus tumor in a 29-year-old woman. Contrast-enhanced CT scan shows a large, complex pelvic mass with solid and cystic components (arrows). Associated ascites is also seen (*). The patient had an elevated serum -fetoprotein level of 58,000 IU/mL (normal range, 0-15 IU/mL).
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Sex Cord–Stromal Tumors
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Gonadal cell types that derive from the coelomic epithelium (sex cords) or mesenchymal cells of the embryonic gonads include granulosa cells, theca cells, fibroblasts, Leydig cells, and Sertolicells. Ovarian tumors composed of these cell types are called sex cord–stromal tumors (Table 1). This group of tumors represents approximately 8% of ovarian neoplasms and affects all age groups. The most common types are granulosa cell tumors, fibrothecomas, and Sertoli-Leydig cell tumors. Sex cord–stromal tumors are of interest partly because of their hormonal effects, which are rare in other ovarian neoplasms (36). The vast majority of sex cord–stromal tumors are either benign (eg, fibrothecoma, sclerosing stromal tumor) or largely confined to the ovary at diagnosis (eg, granulosa cell tumor, Sertoli-Leydig cell tumor) (36).
Granulosa Cell Tumor
Granulosa cell tumor of the ovary is the most common malignant sex cord–stromal tumor as well as the most common estrogen-producing ovarian tumor. Adult granulosa cell tumors are far more common than the juvenile type and account for 95% of all granulosa cell tumors. They occur predominantly in peri- and postmenopausal women. The hyperestrogenemia may produce combined endometrial hyperplasia, polyps, or carcinoma. Endometrial carcinoma is associated with these neoplasms in 3%–25% of cases (36–39). Imaging findings in adult ovarian granulosa cell tumors vary widely and range from solid masses, to tumors with varying degrees of hemorrhagic or fibrotic changes, to multilocular cystic lesions (Fig 20), to completely cystic tumors. Intratumoral bleeding, infarcts, fibrous degeneration, and irregularly arranged tumor cells have yielded heterogeneously solid tumors (37,38). In contrast with epithelial neoplasms, granulosa cell tumors do not have intracystic papillary projections, have less propensity for peritoneal seeding, and are confined to the ovary at the time of diagnosis. Estrogenic effects on the uterus may manifest as uterine enlargement or as endometrial thickening or hemorrhage (Fig 21) (36).
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Figure 20. Granulosa cell tumor in a 55-year-old woman. Contrast-enhanced CT scan shows a large, complex mass with a lobular contour, multiple cysts with a "bunch of grapes" appearance on the right (arrows), and an irregularly enhancing solid portion on the left (*). U = uterus.
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Figure 21a. Granulosa cell tumor in a 71-year-old woman. (a) Sagittal turbo spin-echo T2-weighted MR image (4,275/138) shows a lobulated multilocular cystic mass that resembles a cystadenocarcinoma. However, no evidence of a papillary projection is noted. The endometrial cavity (arrows) is unusually prominent for a patient this age, a finding that is consistent with endometrial hyperplasia. (b) Gadolinium-enhanced fat-suppressed FLASH T1-weighted MR image (148/4.8) demonstrates multiple well-enhanced septa, with numerous large cystic spaces lined by granulosa cells. These findings represent an extreme example of the macrofollicular pattern.
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Figure 21b. Granulosa cell tumor in a 71-year-old woman. (a) Sagittal turbo spin-echo T2-weighted MR image (4,275/138) shows a lobulated multilocular cystic mass that resembles a cystadenocarcinoma. However, no evidence of a papillary projection is noted. The endometrial cavity (arrows) is unusually prominent for a patient this age, a finding that is consistent with endometrial hyperplasia. (b) Gadolinium-enhanced fat-suppressed FLASH T1-weighted MR image (148/4.8) demonstrates multiple well-enhanced septa, with numerous large cystic spaces lined by granulosa cells. These findings represent an extreme example of the macrofollicular pattern.
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Fibrothecoma
Fibroma and thecoma are forms of a spectrum of benign tumors. Lipid-rich thecoma demonstrates estrogenic activity and few fibroblasts. In contrast, fibroma has no thecal cells and demonstrates no estrogenic activity. These tumors occur in both pre- and postmenopausal women. Fibroma is the most common sex cord tumor. It is composed of whorled bundles of cytologically bland, benign, spindle-shaped fibroblasts and collagen (36,40). Ovarian fibromas are important from an imaging standpoint because they appear as solid masses, thereby mimicking malignant neoplasms. They are associated with ascites or Meigs syndrome (7,9). US demonstrates a homogeneous hypoechoic mass with posterior acoustic shadowing. However, a broad spectrum of US features is seen, and in most cases the appearance of the tumor is nonspecific (41). CT shows a homogeneous solid tumor with delayed enhancement (42). Because of their abundant collagen contents, these tumors have low signal intensity on T1-weighted MR images and very low signal intensity on T2-weighted images (Fig 22). These findings are relatively diagnostic for fibroma (40). Dense calcifications are often seen (Fig 22). Scattered high-signal-intensity areas in the mass represent edema or cystic degeneration (Fig 23) (40,42).
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Figure 22a. Fibroma in a 53-year-old woman. (a) Conventional radiograph shows dense amorphous calcification in the pelvic cavity. The initial diagnosis was leiomyoma with dystrophic calcification. (b) Axial turbo spin-echo T1-weighted MR image (800/12) shows a well-defined round mass (M) with extensive low-signal-intensity foci representing calcifications. U = uterus. (c) On an axial turbo spin-echo T2-weighted MR image (5,200/132), the mass (arrows) has low signal intensity with high-signal-intensity foci. A small amount of ascites is present in the cul-de-sac (*).
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Figure 22b. Fibroma in a 53-year-old woman. (a) Conventional radiograph shows dense amorphous calcification in the pelvic cavity. The initial diagnosis was leiomyoma with dystrophic calcification. (b) Axial turbo spin-echo T1-weighted MR image (800/12) shows a well-defined round mass (M) with extensive low-signal-intensity foci representing calcifications. U = uterus. (c) On an axial turbo spin-echo T2-weighted MR image (5,200/132), the mass (arrows) has low signal intensity with high-signal-intensity foci. A small amount of ascites is present in the cul-de-sac (*).
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Figure 22c. Fibroma in a 53-year-old woman. (a) Conventional radiograph shows dense amorphous calcification in the pelvic cavity. The initial diagnosis was leiomyoma with dystrophic calcification. (b) Axial turbo spin-echo T1-weighted MR image (800/12) shows a well-defined round mass (M) with extensive low-signal-intensity foci representing calcifications. U = uterus. (c) On an axial turbo spin-echo T2-weighted MR image (5,200/132), the mass (arrows) has low signal intensity with high-signal-intensity foci. A small amount of ascites is present in the cul-de-sac (*).
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Figure 23a. Fibrothecoma in a 46-year-old woman. (a) Axial turbo spin-echo T1-weighted MR image (800/12) shows a round, low-signal-intensity mass (M) in the right adnexal region. U = uterus. (b) On an axial turbo spin-echo T2-weighted MR image (3,900/99), the mass again demonstrates low signal intensity, with central increased signal intensity that represents edema. U = uterus. (c) Gadolinium-enhanced fat-suppressed T1-weighted MR image (147/4.8) demonstrates peripheral enhancement of the mass with a central edematous area.
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Figure 23b. Fibrothecoma in a 46-year-old woman. (a) Axial turbo spin-echo T1-weighted MR image (800/12) shows a round, low-signal-intensity mass (M) in the right adnexal region. U = uterus. (b) On an axial turbo spin-echo T2-weighted MR image (3,900/99), the mass again demonstrates low signal intensity, with central increased signal intensity that represents edema. U = uterus. (c) Gadolinium-enhanced fat-suppressed T1-weighted MR image (147/4.8) demonstrates peripheral enhancement of the mass with a central edematous area.
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Figure 23c. Fibrothecoma in a 46-year-old woman. (a) Axial turbo spin-echo T1-weighted MR image (800/12) shows a round, low-signal-intensity mass (M) in the right adnexal region. U = uterus. (b) On an axial turbo spin-echo T2-weighted MR image (3,900/99), the mass again demonstrates low signal intensity, with central increased signal intensity that represents edema. U = uterus. (c) Gadolinium-enhanced fat-suppressed T1-weighted MR image (147/4.8) demonstrates peripheral enhancement of the mass with a central edematous area.
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Ovarian masses with fibrous components include fibroma, fibrothecoma, cystadenofibroma, and Brenner tumor. The fibrous components of these masses tend to have very low signal intensity on T2-weighted MR images (7,9). Pedunculated uterine leiomyomas and broad-ligament leiomyomas frequently appear as adnexal or ovarian masses, typically with very low signal intensity on T2-weighted MR images. Subserosal myomas are supplied by the vessels from the uterine arteries that course through the adjacent myometrium and may appear as the vessels that intervene between a myoma and the adjacent uterus. In contrast, ovarian masses are most likely fed directly by the ovarian arteries or by the ovarian branches of the uterine arteries that course along the fallopian tubes. Observation of the interface vessels between the uterus and adnexal masses seems to be useful in differentiating leiomyoma from ovarian fibroma (Fig 24) (43,44).
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Abstract
LEARNING OBJECTIVES FOR TEST...
