A Metastatic Ovarian Tumor Mimicking Pregnancy Luteoma Found during Puerperium

A 28-year-old puerperant with fever came to our hospital. Her last delivery was uneventful. Her laboratory data was normal except for anemia (red blood cell count was 3.41 × 106/μl) and elevated serum C-reactive protein (7.23 mg/dl). CA19-9, CA125, and carcinoembryonic antigen (CEA) were negative. She had no family history indicating hereditary cancer syndrome. Ultrasound revealed a right adnexal mass that was not recognized during the cesarean section. Magnetic resonance (MR) images revealed a well-demarcated mass within a pseudo-cyst surrounded by uterus, pelvic sidewall, and right cardinal ligament. The mass was composed of tiny hypointense nodules within the background of high signal on T2-weighted (T2WI; Fig. 1A) images. Contrast enhanced T1-weighted images revealed strong enhancement of the background stroma and the hypointense nodules remained with weaker enhancement (Fig. 1B, C). There was no signal difference between the two parts on diffusion-weighted images (Fig. 1D). We suspected pregnancy luteoma and sclerosing stromal tumor (SST) as the similarity of pseudolobular pattern. The white-colored small right ovarian mass with hemorrhage surrounded by the pseudo-cyst was removed (Fig. 1E). The tumor was composed of varying types of malignant tumors including signet ring-like cells (Fig. 1F) and was positive for CDX2. The histopathological diagnosis was metastatic adenocarcinoma of the ovary and its peritoneal dissemination. Advanced rectal cancer was also found via colonic fiberscope followed by the surgery. As the disease was resistive against chemotherapy, the patient was transferred to another hospital under best supportive care.