Introduction: Endometriosis is a benign condition characterized by endometrial tissue deposited outside the uterine cavity. Endometriosis characteristics include a well-defined cyst (endometrioma) with or without internal septations and seeding nodules; however, no case of extensive infiltrating abdominopelvic endometriosis have been reported.
Case presentation: A 48-year-old female presented with incidentally found a hypervascular lesion in the pelvic cavity from routine checkup ultrasound. The computed tomography (CT) angiography investigation showed pelvic arteriovenous malformation (AVM). She underwent embolization at interventional radiology unit and the CT angiography follow up showed complete occlusion of pelvic AVM. However, eight months after embolization, she came with severe abdominal pain and hypotension. Emergency CT showed a large abdominopelvic mass with hemoperitoneum which was suspected for gynecologic or peritoneal malignancy. Further magnetic resonance image (MRI) was highly suspicious of peritoneum or mesentery malignancy. Surgical tumor removal was performed. The histologic results were negative for malignancy and the tumor was compatible with endometriosis.
Conclusion: Extensive abdominopelvic endometriosis is rare, and its imaging findings may not exclude peritoneal malignancy. Therefore, a definite diagnosis via histological investigation is necessary.