Endometrioma With Hemorrhagic Ascites Mimicking Ovarian Malignancy: A Case Report.

Endometriosis is a highly prevalent and morbid condition in women of reproductive age, often leading to well-known complications such as infertility, intestinal adhesions, and severe chronic pelvic pain. There is a particular and less frequent entity, even in patients with no prior history of pelvic pain or endometriosis, that presents as a pelvic mass associated with hemorrhagic ascites. This finding can be confused with a malignant ovarian neoplasm, a diagnostic error with unfavorable outcomes and a significant impact on patients' lives. We present the case of a young woman with no prior history of pelvic pain who presented with a right adnexal mass, ascites, pleural effusion, and elevated tumor markers. She underwent a radical hysterectomy with a presumption of an ovarian neoplasm involving the peritoneum. Imaging findings included a right ovarian bilobed lesion with high T2 signal intensity, a shading sign, a fluid-fluid level, and thick walls. The final pathological diagnosis was endometriosis.