Superficial Endometriosis Mimicking Soft Tissue Tumors: A Case Series of Clinical and Characteristic MRI Findings in Eight Patients.

Purpose: Differentiating superficial endometriosis from soft tissue tumor is important because these two conditions required quite different therapeutic strategies. The purpose of this study was to evaluate the radiological imaging findings and clinical features of superficial endometriosis mimicking soft tissue tumor and to clarify the distinction between these two diseases. Patients and Methods: In this retrospective study, 8 women (mean age, 40.1, range, 31-51) who were pathologically diagnosed with endometriosis and underwent excisional biopsy were identified. Demographic, clinical, and radiographic findings were reviewed. Results: All patients had history or coexisting obstetric or gynecologic disorder, such as ovarian cyst, uterine myoma, or cesarean section. Five patients complained of painful mass lesions during menstruation. On magnetic resonance imaging, although 6 of 8 patients exhibited lesions isointense to muscle on both T1- and T2-weighted images, a consistent and diagnostically important finding was the presence of distinct small hyperintense foci within the lesions on both sequences. Only one patient had cystic hyperintense lesion on T2-weighted image with fluid-fluid level feature. Conclusion: We showed the clinical and radiographic findings of superficial endometriosis. Painful mass during menstruation is an important finding distinguishing soft tissue tumor from superficial endometriosis. Magnetic resonance imaging shows small foci or fluid-fluid level and is useful in clarifying the suspicion of superficial endometriosis to avoid misdiagnosis.