Endometriosis on the surface of the uterus mimicking a malignant tumor: A case report with literature review

RATIONALE: The purpose of this case report was to raise awareness regarding endometriosis on the surface of the uterus mimicking malignant tumor and thus manage it accurately. PATIENT CONCERNS: A 40-year-old Asian woman with a 2-year history of lower abdomen pain was admitted to our department with elevated serum cancer antigen (CA) 125 level, weight loss, and pelvic mass from 20 days previously. Magnetic resonance imaging revealed a high volume of effusion in the pelvic cavity, an irregular occupying lesion on the surface of the fundus of the uterus, and multiple nodules. DIAGNOSES: Postoperative pathology confirmed the diagnosis of endometriosis. INTERVENTIONS: Diagnostic laparoscopy revealed large crunchy tissue and soft nodules on the surface of the posterior wall of the uterus and approximately 2000 mL of bloody ascites. The result of the frozen-section analysis of the tissue on the surface of the uterus indicated endometriosis. The surgical procedure was converted to laparotomy due to bleeding after biopsy. OUTCOMES: The patient's recovery was uneventful. Three months after the operation, the patient had a good general state without periodic pain, and the CA125 level returned to normal. LESSONS: A large mass occurring in the pelvic cavity could be indicative of endometriosis, especially if accompanied by a history of period pain. Preoperative positron emission tomography may increase the accuracy of the diagnosis.