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DOI: 10.1148/rg.262055041
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RadioGraphics 2006;26:407-417
© RSNA, 2006

EDUCATION EXHIBIT

Malignant Transformation of Pelvic Endometriosis: MR Imaging Findings and Pathologic Correlation1

Mayumi Takeuchi, MD, PhD, Kenji Matsuzaki, MD, PhD, Hisanori Uehara, MD, PhD and Hiromu Nishitani, MD, PhD

1 From the Departments of Radiology (M.T., K.M., H.N.) and Molecular and Environmental Pathology (H.U.), University of Tokushima, 3-18-15 Kuramoto-cho, Tokushima 770-8503, Japan. Presented as an education exhibit at the 2004 RSNA Annual Meeting. Received March 4, 2005; revision requested June 6 and received June 23; accepted June 29. All authors have no financial relationships to disclose. Address correspondence to M.T. (e-mail: mayumi{at}clin.med.tokushima-u.ac.jp).


   Abstract
Top
 Abstract
Introduction
 Pathologic Features
 MR Imaging Findings
 Malignant Transformation of...
 Endometriosis-associated...
 Value of Subtraction Imaging
 Pitfalls
 Summary
 References
 
Malignant transformation is a rare complication of endometriosis. Endometriosis-associated ovarian cancers are seen more often in younger women than are ovarian cancers without endometriosis, and early detection is important to improve the prognosis and preserve fertility. However, normal decidual change of the ectopic endometrium in an endometrioma during pregnancy must be differentiated from malignant transformation. The finding that is most important for a diagnosis of malignant change is the presence of one or more contrast material–enhanced mural nodules within a cystic mass at magnetic resonance (MR) imaging. Dynamic subtraction MR imaging is useful in depicting small contrast-enhanced nodules within the hyperintense endometrioma on T1-weighted images. Intracystic coagulate may mimic a mural nodule; the absence of contrast enhancement is the diagnostic clue to its benignity. Enlargement of the endometrioma and the disappearance of shading within the mass on T2-weighted images are suggestive of malignant transformation.

© RSNA, 2006


   Introduction
Top
 Abstract
 Introduction
Pathologic Features
 MR Imaging Findings
 Malignant Transformation of...
 Endometriosis-associated...
 Value of Subtraction Imaging
 Pitfalls
 Summary
 References
 
Malignant transformation is a rare complication of endometriosis and is estimated to occur in 0.6%–0.8% of women with ovarian endometriosis (1–3). Endometriosis-associated ovarian cancer generally affects women who are 10–20 years younger than those affected by ovarian cancer without endometriosis, and early detection is important to improve the prognosis and preserve fertility (1). The pathogenesis of malignant transformation of endometriosis is still unclear, but estrogen may play a role, so endometriosis should be treated or monitored closely in women of reproductive age (1,4). This article demonstrates imaging findings of malignant transformation of pelvic endometriosis and describes the diagnostic clues that enable differentiation of malignant endometrial lesions from benign endometriomas.


   Pathologic Features
Top
 Abstract
 Introduction
 Pathologic Features
MR Imaging Findings
 Malignant Transformation of...
 Endometriosis-associated...
 Value of Subtraction Imaging
 Pitfalls
 Summary
 References
 
Sampson first reported some cases of malignant tumors that were diagnosed in women with endometriosis in 1925 (5). Since then, malignant transformation has come to be recognized as a rare complication of endometriosis. The coexistence of endometriosis and carcinoma with a transitional lesion in the same ovary is a definitive pathologic finding of malignant transformation but is not observed in all cases (6). A cluster of hemosiderin-laden macrophages within a thick fibrous capsule that contains chocolate-colored hemorrhagic material is suggestive of a cystic endometrial tumor (Fig 1). Endometrioid tumors of the ovary and clear cell adenocarcinomas are histologic types of tumors that commonly occur in ovarian endometriosis (1,7).


Figure 1
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  		Figure 1a.  Malignant transformation of right-sided endometrioma in a 42-year-old woman. (a) Photomicrograph of a histopathologic specimen shows endometrial glands (*) outside the fibrous capsule of the cyst (FC), and hemorrhagic material inside the cystic lumen (L). (b) Photomicrograph of a histopathologic specimen shows clear cell carcinoma (C) and a cluster of hemosiderin-laden macrophages (arrows) within the thick fibrous capsule (FC).

 

Figure 1
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  		Figure 1b.  Malignant transformation of right-sided endometrioma in a 42-year-old woman. (a) Photomicrograph of a histopathologic specimen shows endometrial glands (*) outside the fibrous capsule of the cyst (FC), and hemorrhagic material inside the cystic lumen (L). (b) Photomicrograph of a histopathologic specimen shows clear cell carcinoma (C) and a cluster of hemosiderin-laden macrophages (arrows) within the thick fibrous capsule (FC).

 

   MR Imaging Findings
Top
 Abstract
 Introduction
 Pathologic Features
 MR Imaging Findings
Malignant Transformation of...
 Endometriosis-associated...
 Value of Subtraction Imaging
 Pitfalls
 Summary
 References
 
Multiple hyperintense cysts on T1-weighted images, or a cyst with signal hyperintensity on T1-weighted images and hypointensity on T2-weighted images and with an appearance of shading that reflects the presence of high concentrations of methemoglobin, protein, and iron products due to repeated menstrual bleeding, are definitive criteria for a diagnosis of ovarian endometrial cyst on the basis of magnetic resonance (MR) imaging (8) (Fig 2). At contrast material–enhanced MR imaging, the peripheral low-signal-intensity rim, which represents the thick fibrous capsule of the cyst, shows intense contrast enhancement. Large endometrial cysts may contain clots or thin septa. A hematocrit effect is occasionally observed (9). Additional T1-weighted fat-saturated acquisitions may be useful for detecting small peritoneal tumor implants and for differentiating endometrial cysts from dermoid cysts (10,11).


Figure 2
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  		Figure 2a.  Bilateral endometriomas in a 21-year-old woman. (a) Axial T2-weighted fast spin-echo MR image (repetition time msec/echo time msec, 4000/105) shows bilateral adnexal masses with extensive shading, findings that represent endometriomas. (b) Axial T1-weighted spin-echo MR image (500/14) shows the endometriomas with high signal intensity. (c) Axial T1-weighted fat-saturated spin-echo MR image (500/14) shows no reduction of signal in the endometriomas. (d) Photograph of the resected specimen shows a cystic mass that contains chocolate-colored hemorrhagic material.

 

Figure 2
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  		Figure 2b.  Bilateral endometriomas in a 21-year-old woman. (a) Axial T2-weighted fast spin-echo MR image (repetition time msec/echo time msec, 4000/105) shows bilateral adnexal masses with extensive shading, findings that represent endometriomas. (b) Axial T1-weighted spin-echo MR image (500/14) shows the endometriomas with high signal intensity. (c) Axial T1-weighted fat-saturated spin-echo MR image (500/14) shows no reduction of signal in the endometriomas. (d) Photograph of the resected specimen shows a cystic mass that contains chocolate-colored hemorrhagic material.

 

Figure 2
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  		Figure 2c.  Bilateral endometriomas in a 21-year-old woman. (a) Axial T2-weighted fast spin-echo MR image (repetition time msec/echo time msec, 4000/105) shows bilateral adnexal masses with extensive shading, findings that represent endometriomas. (b) Axial T1-weighted spin-echo MR image (500/14) shows the endometriomas with high signal intensity. (c) Axial T1-weighted fat-saturated spin-echo MR image (500/14) shows no reduction of signal in the endometriomas. (d) Photograph of the resected specimen shows a cystic mass that contains chocolate-colored hemorrhagic material.

 

Figure 2
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  		Figure 2d.  Bilateral endometriomas in a 21-year-old woman. (a) Axial T2-weighted fast spin-echo MR image (repetition time msec/echo time msec, 4000/105) shows bilateral adnexal masses with extensive shading, findings that represent endometriomas. (b) Axial T1-weighted spin-echo MR image (500/14) shows the endometriomas with high signal intensity. (c) Axial T1-weighted fat-saturated spin-echo MR image (500/14) shows no reduction of signal in the endometriomas. (d) Photograph of the resected specimen shows a cystic mass that contains chocolate-colored hemorrhagic material.

 

   Malignant Transformation of Endometrioma
Top
 Abstract
 Introduction
 Pathologic Features
 MR Imaging Findings
 Malignant Transformation of...
Endometriosis-associated...
 Value of Subtraction Imaging
 Pitfalls
 Summary
 References
 
Contrast-enhanced mural nodules observed in an endometrioma on T1-weighted images after the administration of a contrast medium are suggestive of malignancy. The mass in such a case must be removed (12) (Fig 3). The disappearance of shading in the mass on T2-weighted images, a finding that may be due to the dilution of thick hemorrhagic fluid by tumor secretions or to interval enlargement of the endometrial cyst, may suggest malignant transformation (12) (Fig 3); however, the same characteristic may be observed also in benign endometrial cysts.


Figure 3
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  		Figure 3a.  Malignant transformation of a left-sided ovarian endometrioma in a 40-year-old woman. (a) Sagittal T2-weighted fast spin-echo MR image (3500/95) shows a left adnexal cystic mass with a slightly hyperintense mural nodule (arrow). (b) Sagittal T1-weighted spin-echo MR image (300/9) shows a hyperintense cystic mass with a hypointense mural nodule (arrow). (c) Sagittal contrast-enhanced T1-weighted gradient-echo MR image (100/1.6) shows enhancement of the mural nodule (arrow). Clear cell carcinoma was proved at surgery. (d) Axial T2-weighted fast spin-echo MR image (3600/90), obtained 2 years before a, b, and c, shows a left adnexal cystic mass with shading indicative of a benign endometrioma. (e) Axial T2-weighted fast spin-echo MR image (4800/88), obtained 2 years after a, shows a slightly hypointense mural nodule (arrow) and an absence of shading in the mass.

 

Figure 3
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  		Figure 3b.  Malignant transformation of a left-sided ovarian endometrioma in a 40-year-old woman. (a) Sagittal T2-weighted fast spin-echo MR image (3500/95) shows a left adnexal cystic mass with a slightly hyperintense mural nodule (arrow). (b) Sagittal T1-weighted spin-echo MR image (300/9) shows a hyperintense cystic mass with a hypointense mural nodule (arrow). (c) Sagittal contrast-enhanced T1-weighted gradient-echo MR image (100/1.6) shows enhancement of the mural nodule (arrow). Clear cell carcinoma was proved at surgery. (d) Axial T2-weighted fast spin-echo MR image (3600/90), obtained 2 years before a, b, and c, shows a left adnexal cystic mass with shading indicative of a benign endometrioma. (e) Axial T2-weighted fast spin-echo MR image (4800/88), obtained 2 years after a, shows a slightly hypointense mural nodule (arrow) and an absence of shading in the mass.

 

Figure 3
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  		Figure 3c.  Malignant transformation of a left-sided ovarian endometrioma in a 40-year-old woman. (a) Sagittal T2-weighted fast spin-echo MR image (3500/95) shows a left adnexal cystic mass with a slightly hyperintense mural nodule (arrow). (b) Sagittal T1-weighted spin-echo MR image (300/9) shows a hyperintense cystic mass with a hypointense mural nodule (arrow). (c) Sagittal contrast-enhanced T1-weighted gradient-echo MR image (100/1.6) shows enhancement of the mural nodule (arrow). Clear cell carcinoma was proved at surgery. (d) Axial T2-weighted fast spin-echo MR image (3600/90), obtained 2 years before a, b, and c, shows a left adnexal cystic mass with shading indicative of a benign endometrioma. (e) Axial T2-weighted fast spin-echo MR image (4800/88), obtained 2 years after a, shows a slightly hypointense mural nodule (arrow) and an absence of shading in the mass.

 

Figure 3
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  		Figure 3d.  Malignant transformation of a left-sided ovarian endometrioma in a 40-year-old woman. (a) Sagittal T2-weighted fast spin-echo MR image (3500/95) shows a left adnexal cystic mass with a slightly hyperintense mural nodule (arrow). (b) Sagittal T1-weighted spin-echo MR image (300/9) shows a hyperintense cystic mass with a hypointense mural nodule (arrow). (c) Sagittal contrast-enhanced T1-weighted gradient-echo MR image (100/1.6) shows enhancement of the mural nodule (arrow). Clear cell carcinoma was proved at surgery. (d) Axial T2-weighted fast spin-echo MR image (3600/90), obtained 2 years before a, b, and c, shows a left adnexal cystic mass with shading indicative of a benign endometrioma. (e) Axial T2-weighted fast spin-echo MR image (4800/88), obtained 2 years after a, shows a slightly hypointense mural nodule (arrow) and an absence of shading in the mass.

 

Figure 3
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  		Figure 3e.  Malignant transformation of a left-sided ovarian endometrioma in a 40-year-old woman. (a) Sagittal T2-weighted fast spin-echo MR image (3500/95) shows a left adnexal cystic mass with a slightly hyperintense mural nodule (arrow). (b) Sagittal T1-weighted spin-echo MR image (300/9) shows a hyperintense cystic mass with a hypointense mural nodule (arrow). (c) Sagittal contrast-enhanced T1-weighted gradient-echo MR image (100/1.6) shows enhancement of the mural nodule (arrow). Clear cell carcinoma was proved at surgery. (d) Axial T2-weighted fast spin-echo MR image (3600/90), obtained 2 years before a, b, and c, shows a left adnexal cystic mass with shading indicative of a benign endometrioma. (e) Axial T2-weighted fast spin-echo MR image (4800/88), obtained 2 years after a, shows a slightly hypointense mural nodule (arrow) and an absence of shading in the mass.

 

   Endometriosis-associated Carcinoma
Top
 Abstract
 Introduction
 Pathologic Features
 MR Imaging Findings
 Malignant Transformation of...
 Endometriosis-associated...
Value of Subtraction Imaging
 Pitfalls
 Summary
 References
 
The typical morphologic appearance of an endometriosis-associated carcinoma is that of a unilateral large cystic mass that contains hemorrhagic fluid and mural nodules. The mural nodules appear contrast enhanced on postcontrast T1-weighted images (12) (Fig 4). The signal intensity of mural nodules is low on T1-weighted images and variable on T2-weighted images (Fig 5). The signal intensity on T2-weighted images and the shape of mural nodules are not related to the histologic subtype of the carcinoma (12). Usually, cystic components of the mass appear hyperintense on both T1- and T2-weighted images. Shading within the mass is rarely observed on T2-weighted images (12) (Fig 6).


Figure 4
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  		Figure 4a.  Malignant transformation of a right-sided ovarian endometrioma in a 59-year-old woman. (a) Axial contrast-enhanced T1-weighted fat-saturated spin-echo MR image (550/9) shows a hyperintense right adnexal cystic mass with contrast-enhanced mural nodules. (b) Photograph of the resected specimen shows a cystic mass with nodular components. (c, d) Photomicrographs of histopathologic specimens show clear cell carcinoma with various morphologic features and cell types, including clear cells (c) and hobnail cells (arrows in d).

 

Figure 4
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  		Figure 4b.  Malignant transformation of a right-sided ovarian endometrioma in a 59-year-old woman. (a) Axial contrast-enhanced T1-weighted fat-saturated spin-echo MR image (550/9) shows a hyperintense right adnexal cystic mass with contrast-enhanced mural nodules. (b) Photograph of the resected specimen shows a cystic mass with nodular components. (c, d) Photomicrographs of histopathologic specimens show clear cell carcinoma with various morphologic features and cell types, including clear cells (c) and hobnail cells (arrows in d).

 

Figure 4
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  		Figure 4c.  Malignant transformation of a right-sided ovarian endometrioma in a 59-year-old woman. (a) Axial contrast-enhanced T1-weighted fat-saturated spin-echo MR image (550/9) shows a hyperintense right adnexal cystic mass with contrast-enhanced mural nodules. (b) Photograph of the resected specimen shows a cystic mass with nodular components. (c, d) Photomicrographs of histopathologic specimens show clear cell carcinoma with various morphologic features and cell types, including clear cells (c) and hobnail cells (arrows in d).

 

Figure 4
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  		Figure 4d.  Malignant transformation of a right-sided ovarian endometrioma in a 59-year-old woman. (a) Axial contrast-enhanced T1-weighted fat-saturated spin-echo MR image (550/9) shows a hyperintense right adnexal cystic mass with contrast-enhanced mural nodules. (b) Photograph of the resected specimen shows a cystic mass with nodular components. (c, d) Photomicrographs of histopathologic specimens show clear cell carcinoma with various morphologic features and cell types, including clear cells (c) and hobnail cells (arrows in d).

 

Figure 5
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  		Figure 5a.  Malignant transformation of a left-sided ovarian endometrioma in a 65-year-old woman. (a) Axial T1-weighted spin-echo MR image (466/14) shows a left adnexal, slightly hyperintense, large cystic mass with mural nodules. (b) Sagittal T2-weighted fast spin-echo MR image (4200/96) shows the cystic mass with high signal intensity and the mural nodules with heterogeneous signal intensity. The histologic diagnosis was poorly differentiated adenocarcinoma.

 

Figure 5
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  		Figure 5b.  Malignant transformation of a left-sided ovarian endometrioma in a 65-year-old woman. (a) Axial T1-weighted spin-echo MR image (466/14) shows a left adnexal, slightly hyperintense, large cystic mass with mural nodules. (b) Sagittal T2-weighted fast spin-echo MR image (4200/96) shows the cystic mass with high signal intensity and the mural nodules with heterogeneous signal intensity. The histologic diagnosis was poorly differentiated adenocarcinoma.

 

Figure 6
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  		Figure 6a.  Malignant transformation of a left-sided ovarian endometrioma in a 46-year-old woman. (a) Sagittal T2-weighted fast spin-echo MR image (3400/120) shows a large left adnexal cystic mass with hypointense signal and shading and with a hyperintense mural nodule. (b) Sagittal T1-weighted spin-echo MR image (600/24) shows the cystic mass with high signal intensity. (c) Sagittal contrast-enhanced T1-weighted spin-echo MR image (600/24) shows enhancement of the mural nodule (arrow). The histologic diagnosis was endometrioid adenocarcinoma.

 

Figure 6
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  		Figure 6b.  Malignant transformation of a left-sided ovarian endometrioma in a 46-year-old woman. (a) Sagittal T2-weighted fast spin-echo MR image (3400/120) shows a large left adnexal cystic mass with hypointense signal and shading and with a hyperintense mural nodule. (b) Sagittal T1-weighted spin-echo MR image (600/24) shows the cystic mass with high signal intensity. (c) Sagittal contrast-enhanced T1-weighted spin-echo MR image (600/24) shows enhancement of the mural nodule (arrow). The histologic diagnosis was endometrioid adenocarcinoma.

 

Figure 6
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  		Figure 6c.  Malignant transformation of a left-sided ovarian endometrioma in a 46-year-old woman. (a) Sagittal T2-weighted fast spin-echo MR image (3400/120) shows a large left adnexal cystic mass with hypointense signal and shading and with a hyperintense mural nodule. (b) Sagittal T1-weighted spin-echo MR image (600/24) shows the cystic mass with high signal intensity. (c) Sagittal contrast-enhanced T1-weighted spin-echo MR image (600/24) shows enhancement of the mural nodule (arrow). The histologic diagnosis was endometrioid adenocarcinoma.

 

   Value of Subtraction Imaging
Top
 Abstract
 Introduction
 Pathologic Features
 MR Imaging Findings
 Malignant Transformation of...
 Endometriosis-associated...
 Value of Subtraction Imaging
Pitfalls
 Summary
 References
 
Hyperintense hemorrhagic fluid on T1-weighted images may mask the contrast enhancement of small mural nodules (Fig 7). Contrast-enhanced subtraction images are helpful for evaluating the degree of enhancement of such nodules (12) (Figs 8, 9). Contrast-enhanced dynamic subtraction images obtained with a gradient-echo sequence are particularly useful for this purpose (12) (Fig 9).


Figure 7
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  		Figure 7a.  Malignant transformation of a left-sided ovarian endometrioma in a 73-year-old woman. (a) Sagittal T2-weighted fast spin-echo MR image (4000/120) shows a left adnexal cystic mass with a hypointense clot. (b) Sagittal contrast-enhanced T1-weighted fat-saturated spin-echo MR image (572/15) shows a hyperintense cystic mass with no enhanced mural nodules. A small mural nodule was found subsequently at surgery. The histologic diagnosis was clear cell carcinoma.

 

Figure 7
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  		Figure 7b.  Malignant transformation of a left-sided ovarian endometrioma in a 73-year-old woman. (a) Sagittal T2-weighted fast spin-echo MR image (4000/120) shows a left adnexal cystic mass with a hypointense clot. (b) Sagittal contrast-enhanced T1-weighted fat-saturated spin-echo MR image (572/15) shows a hyperintense cystic mass with no enhanced mural nodules. A small mural nodule was found subsequently at surgery. The histologic diagnosis was clear cell carcinoma.

 

Figure 8
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  		Figure 8a.  Right-sided ovarian endometriomas in a 26-year-old woman. (a) Axial T1-weighted spin-echo MR image (450/9) shows right adnexal cystic masses with high signal intensity that represent endometriomas. (b) Axial contrast-enhanced T1-weighted fat-saturated spin-echo MR image (550/9) shows intracystic high signal intensity sufficient to mask the contrast enhancement of any mural nodule that may be present. A large intracystic clot (arrow) shows no contrast enhancement. (c) Axial dynamic subtraction MR image synthesized from data obtained with both unenhanced MR imaging and with contrast-enhanced MR imaging with a dynamic sequence (gradient echo, 130/1.9) shows enhancement of the fibrous capsule around the cysts but no enhanced mural nodules.

 

Figure 8
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  		Figure 8b.  Right-sided ovarian endometriomas in a 26-year-old woman. (a) Axial T1-weighted spin-echo MR image (450/9) shows right adnexal cystic masses with high signal intensity that represent endometriomas. (b) Axial contrast-enhanced T1-weighted fat-saturated spin-echo MR image (550/9) shows intracystic high signal intensity sufficient to mask the contrast enhancement of any mural nodule that may be present. A large intracystic clot (arrow) shows no contrast enhancement. (c) Axial dynamic subtraction MR image synthesized from data obtained with both unenhanced MR imaging and with contrast-enhanced MR imaging with a dynamic sequence (gradient echo, 130/1.9) shows enhancement of the fibrous capsule around the cysts but no enhanced mural nodules.

 

Figure 8
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  		Figure 8c.  Right-sided ovarian endometriomas in a 26-year-old woman. (a) Axial T1-weighted spin-echo MR image (450/9) shows right adnexal cystic masses with high signal intensity that represent endometriomas. (b) Axial contrast-enhanced T1-weighted fat-saturated spin-echo MR image (550/9) shows intracystic high signal intensity sufficient to mask the contrast enhancement of any mural nodule that may be present. A large intracystic clot (arrow) shows no contrast enhancement. (c) Axial dynamic subtraction MR image synthesized from data obtained with both unenhanced MR imaging and with contrast-enhanced MR imaging with a dynamic sequence (gradient echo, 130/1.9) shows enhancement of the fibrous capsule around the cysts but no enhanced mural nodules.

 

Figure 9
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  		Figure 9a.  Malignant transformation of a left-sided ovarian endometrioma in a 40-year-old woman. (a) Unenhanced MR image obtained with a dynamic sequence (gradient echo, 130/1.9) shows a slightly hyperintense left adnexal mass. (b) Axial dynamic contrast-enhanced MR image obtained 90 seconds after the administration of contrast material shows an enhanced mural nodule (arrow). (c) Axial dynamic subtraction MR image synthesized from a and b shows the enhanced mural nodule (arrow) more clearly.

 

Figure 9
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  		Figure 9b.  Malignant transformation of a left-sided ovarian endometrioma in a 40-year-old woman. (a) Unenhanced MR image obtained with a dynamic sequence (gradient echo, 130/1.9) shows a slightly hyperintense left adnexal mass. (b) Axial dynamic contrast-enhanced MR image obtained 90 seconds after the administration of contrast material shows an enhanced mural nodule (arrow). (c) Axial dynamic subtraction MR image synthesized from a and b shows the enhanced mural nodule (arrow) more clearly.

 

Figure 9
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  		Figure 9c.  Malignant transformation of a left-sided ovarian endometrioma in a 40-year-old woman. (a) Unenhanced MR image obtained with a dynamic sequence (gradient echo, 130/1.9) shows a slightly hyperintense left adnexal mass. (b) Axial dynamic contrast-enhanced MR image obtained 90 seconds after the administration of contrast material shows an enhanced mural nodule (arrow). (c) Axial dynamic subtraction MR image synthesized from a and b shows the enhanced mural nodule (arrow) more clearly.

 

   Pitfalls
Top
 Abstract
 Introduction
 Pathologic Features
 MR Imaging Findings
 Malignant Transformation of...
 Endometriosis-associated...
 Value of Subtraction Imaging
 Pitfalls
Summary
 References
 
The adjacent ovarian parenchyma may be mistaken for a contrast-enhanced solid malignant component in an endometrial cyst. An extracystic crescent-shaped lesion, which may contain follicles, is the characteristic finding in such cases (Fig 10). Intracystic blood clots may show various levels of signal intensity and thus mimic malignant mural nodules; however, the lack of contrast enhancement is a clue to their identity (12) (Fig 11). Decidual changes of the ectopic endometrium in the endometrial cyst during pregnancy also may mimic malignant mural nodules. Broad-based hyperintense mural nodules on T2-weighted images are characteristic of decidual changes, and, in the presence of such findings, close follow-up is necessary to exclude the possibility of malignancy (13) (Fig 12).


Figure 10
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  		Figure 10a.  Left-sided ovarian endometrioma in a 28-year-old woman. (a) Axial T1-weighted spin-echo MR image (500/14) shows a hyperintense left adnexal cystic mass with a hypointense crescent-shaped component (arrow). (b) Axial contrast-enhanced T1-weighted fat-saturated spin-echo MR image (800/14) shows no signal reduction in the cystic mass, while the signal is enhanced in the crescent-shaped component (arrow). (c) Axial T2-weighted fast spin-echo MR image (3500/105) shows heterogeneous signal intensity in the mass and a slightly hyperintense signal in the crescent-shaped component, which contains a follicle (arrow) and represents ovarian parenchyma.

 

Figure 10
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  		Figure 10b.  Left-sided ovarian endometrioma in a 28-year-old woman. (a) Axial T1-weighted spin-echo MR image (500/14) shows a hyperintense left adnexal cystic mass with a hypointense crescent-shaped component (arrow). (b) Axial contrast-enhanced T1-weighted fat-saturated spin-echo MR image (800/14) shows no signal reduction in the cystic mass, while the signal is enhanced in the crescent-shaped component (arrow). (c) Axial T2-weighted fast spin-echo MR image (3500/105) shows heterogeneous signal intensity in the mass and a slightly hyperintense signal in the crescent-shaped component, which contains a follicle (arrow) and represents ovarian parenchyma.

 

Figure 10
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  		Figure 10c.  Left-sided ovarian endometrioma in a 28-year-old woman. (a) Axial T1-weighted spin-echo MR image (500/14) shows a hyperintense left adnexal cystic mass with a hypointense crescent-shaped component (arrow). (b) Axial contrast-enhanced T1-weighted fat-saturated spin-echo MR image (800/14) shows no signal reduction in the cystic mass, while the signal is enhanced in the crescent-shaped component (arrow). (c) Axial T2-weighted fast spin-echo MR image (3500/105) shows heterogeneous signal intensity in the mass and a slightly hyperintense signal in the crescent-shaped component, which contains a follicle (arrow) and represents ovarian parenchyma.

 

Figure 11
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  		Figure 11a.  Bilateral ovarian endometriomas in a 36-year-old woman. (a) Axial T1-weighted spin-echo MR image (400/9) shows hyperintense pelvic cystic masses. (b) Axial T2-weighted fast spin-echo MR image (3600/89) shows a large heterogeneous masslike structure within one of the cysts (arrow). (c) Axial dynamic subtraction MR image synthesized from unenhanced MR image data and contrast-enhanced MR image data obtained with a dynamic sequence (gradient echo, 130/2.1) shows contrast enhancement of the fibrous capsule around the cyst but no enhancement of the masslike structure, which represents a blood clot.

 

Figure 11
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  		Figure 11b.  Bilateral ovarian endometriomas in a 36-year-old woman. (a) Axial T1-weighted spin-echo MR image (400/9) shows hyperintense pelvic cystic masses. (b) Axial T2-weighted fast spin-echo MR image (3600/89) shows a large heterogeneous masslike structure within one of the cysts (arrow). (c) Axial dynamic subtraction MR image synthesized from unenhanced MR image data and contrast-enhanced MR image data obtained with a dynamic sequence (gradient echo, 130/2.1) shows contrast enhancement of the fibrous capsule around the cyst but no enhancement of the masslike structure, which represents a blood clot.

 

Figure 11
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  		Figure 11c.  Bilateral ovarian endometriomas in a 36-year-old woman. (a) Axial T1-weighted spin-echo MR image (400/9) shows hyperintense pelvic cystic masses. (b) Axial T2-weighted fast spin-echo MR image (3600/89) shows a large heterogeneous masslike structure within one of the cysts (arrow). (c) Axial dynamic subtraction MR image synthesized from unenhanced MR image data and contrast-enhanced MR image data obtained with a dynamic sequence (gradient echo, 130/2.1) shows contrast enhancement of the fibrous capsule around the cyst but no enhancement of the masslike structure, which represents a blood clot.

 

Figure 12
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  		Figure 12.  Decidual change of the ectopic endometrium in a right-sided ovarian endometrioma in a 20-year-old pregnant woman. Sagittal T2-weighted fast spin-echo MR image (3300/102) shows a cystic mass with broad-based hyperintense mural nodules (arrow) behind the uterus.

 

   Summary
Top
 Abstract
 Introduction
 Pathologic Features
 MR Imaging Findings
 Malignant Transformation of...
 Endometriosis-associated...
 Value of Subtraction Imaging
 Pitfalls
 Summary
References
 
The appearance of contrast-enhanced mural nodules is the most important finding for a diagnosis of malignant transformation of endometrioma on the basis of MR images. Dynamic subtraction MR imaging is useful for detecting small contrast-enhanced nodules in the hyperintense endometrioma on T1-weighted images. Enlargement of the endometrioma with the disappearance of shading on T2-weighted images is suggestive of malignant transformation. Normal adjacent ovarian parenchyma, intracystic coagulate, and decidual change of the endometrium in an endometrioma during pregnancy should be differentiated from malignant transformation.


   References
Top
 Abstract
 Introduction
 Pathologic Features
 MR Imaging Findings
 Malignant Transformation of...
 Endometriosis-associated...
 Value of Subtraction Imaging
 Pitfalls
 Summary
 References
 

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