E2390. Endometriomas: An Image-Based Review of Typical and Atypical Presentations, Differential Diagnosis and Complications
  1. Matheus Gomes; Universidade Federal de São Paulo (Unifesp)
  2. Cássia Guimarães; Alta Excelência Diagnóstica/DASA; Universidade Federal de São Paulo (Unifesp)
  3. Aldo Alves; Alta Excelência Diagnóstica/DASA; Universidade Federal de São Paulo (Unifesp)
  4. Ulysses Torres; Fleury Medicina e Saúde
  5. Leandro de Mattos; Alta Excelência Diagnóstica/DASA; Universidade Federal de São Paulo (Unifesp)
  6. Ana Paula Moura; Fleury Medicina e Saúde; Santa Casa de Misericórdia de São Paulo
  7. Giuseppe D'Ippolito; Fleury Medicina e Saúde; Universidade Federal de São Paulo (Unifesp)
Endometriomas represent a localized form of endometriosis in the ovaries and tend to have typical radiological patterns. However, they can vary over the course of their evolution and often present complications, such as malignancy, overlapping infection, spontaneous rupture, among others, which are not always associated to a significant clinical setting. Therefore, the radiologist may be aware of these conditions and be familiar with their main differential diagnoses, summarized in an illustrative way in this panel.

Educational Goals / Teaching Points
1. To review typical and atypical imaging features of endometriomas, mainly on magnetic resonance imaging (MRI). 2. To show their main differential diagnosis. 3. To discuss complicated forms of endometriomas, including clinical presentation, risk factors and imaging findings.

Key Anatomic/Physiologic Issues and Imaging Findings/Techniques
T2 shading and dark spot MRI signs reflect chronic cyclical bleeding within an endometrioma, with high sensitivity and specificity respectively (1). Malignant transformation from ovarian endometriosis is rare, and MRI findings could demonstrate contrast enhanced mural nodules, and an enlarged endometrioma with disappearance of shading on T2-weighted imaging (2). The rupture of an endometrioma has an estimated incidence of less than 3% and occurs more commonly in large lesions during pregnancy, due to hormonal stimulation of endometrial stromal elements (3). An MRI feature that may be specific for decidualized endometriosis is a T2 hyperintense mural nodule, which is isointense to the thickened decidualized endometrium. After termination of a pregnancy, decidualized endometriosis has been reported to either resolve or regress to uncomplicated endometriomas (4).

Take-home messages: -Typical MRI findings of an endometrioma include T1 hyperintensity, T2 shading and dark spot sign. -The incidence of complications, such as malignant degeneration, superinfection, decidualization and spontaneous rupture is rare, usually less than 5%, and not always accompanied by symptoms. -Endometrioid and clear cell carcinoma are the two main malignant histological subtypes arising from an endometrioma. -In addition to the hemorrhagic cyst, the main differential diagnosis includes tube-ovarian abscess and some low-grade epithelial and germline neoplasms.