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Reproductive/Endocrine Imaging

E2835. The Many Faces of Endometriosis: MRI Spectrum From Benign to Neoplastic

Sakala M,  Wasnik A,  Bryant B,  Maturen K. University of Michigan, Ann Arbor, MI

Address correspondence to M. Sakala (misakala@med.umich.edu)

Background Information: This exhibit will review the MRI appearance of the various forms of endometriosis. Endometriosis is the extrauterine implantation of endometrial tissue, and MRI is useful for identifying benign hemorrhagic features, extent of implants and deeply infiltrative lesions, and neoplastic transformation.

Educational Goals/Teaching Points: The goals of this exhibit are to understand the pathologic basis of endometriosis, describe various forms of endometriosis including cysts, peritoneal and extraperitoneal implants, and polypoid and deep infiltrative endometriosis, and recognize the MRI appearance of endometriosis including varying morphology, signal characteristics, and secondary signs. We will also identify malignant features in endometriotic lesions.

Key Anatomic/Physiologic Issues and Imaging Findings/Techniques: Several theories exist regarding the origins of endometriosis including retrograde menstruation and metaplastic transformation of peritoneum. Endometriotic ovarian cysts, or endometriomas, have T1-weighted imaging (T1WI) “light bulb” bright or hyperintense signal intensity (SI), T2-weighted imaging (T2WI) “shading” or T2WI hypointensity with or without layering gradient, and restrict diffusion. They are often multiple and bilateral. Endometriotic deposits are solid masslike deposits in the peritoneum and in surgical scars. Fibrotic changes and masslike muscular hyperplasia result. SI is similar to smooth muscle with T2WI hypointense SI, intermediate T1WI SI, and minimal enhancement. Cystic ectopic endometrial glands can be present with or without hemorrhagic contents. Deep infiltrative endometriosis is when endometriotic deposits invade uterosacral and round ligaments, organs, and surgical scars more than 5 mm from the peritoneal surface. Organ invasion commonly includes the posterior uterus, bowel, bladder, and ureters. Polypoid endometriosis is a polypoid masslike infiltration into pelvic organs and neural foramina. The masses are hyperintense on T2WI, can have a hypointense rim on T2WI, and restrict diffusion. Neoplasms occur in 1% of endometriotic lesions, which include clear cell, endometrioid carcinoma, and adenosarcoma, and are detected by enhancing nodularity within an endometriotic lesion. Lymphatic and vascular metastatic spread can be present. Secondary signs of endometriosis include hydrosalpinx or hematosalpinx or evidence of obstructed antegrade menstrual flow.

Conclusion: Endometriosis is the extrauterine implantation of endometrial tissue manifesting in various forms including cysts, peritoneal and extraperitoneal implants, and polypoid and deep infiltrative endometriosis. MRI is useful for identifying hemorrhagic contents, extent of implants, and deeply infiltrative lesions, as well evaluation for potential neoplastic transformation.