MRI and FDG PET/CT findings for small cell neuroendocrine carcinoma of the ovary: a case report and literature review

Ovarian small cell neuroendocrine carcinoma (OSCNEC) is rare and few cases have been reported, which makes preoperative diagnosis difficult. Moreover, no reports have yet described detailed imaging findings or findings of positron emission tomography with fluorine-18 fluorodeoxyglucose (18F-FDG-PET). Therefore, here we report a case of OSCNEC including detailed imaging findings and a literature review. A 74-year-old woman with clinical symptoms of abdominal distension was referred to our hospital because of a pelvic mass detected by ultrasonography at another hospital. Serum levels of cancer antigen 125 and neuron-specific enolase (NSE) were both elevated, at 203.0 U/mL (normal range 0-35.0 U/ml) and 47.6 ng/ml (normal range 0-16.3 ng/ml), respectively. Magnetic resonance imaging at 3.0 Tesla showed a multilocular cystic tumor 18 cm in diameter in the pelvic cavity. The tumor had irregular septa and included a solid component. The cystic component showed partially high intensity suggesting hemorrhage on fat-suppressed T1WI. The solid component showed high intensity on diffusion-weighted imaging and contrast enhancement on contrast-enhanced fat-suppressed T1WI. Irregular peritoneal thickening and nodules suggesting peritoneal dissemination were also detected. 18F-FDG-PET/computed tomography (PET/CT) revealed high FDG uptake (maximum standardized uptake value: 13.0) in the solid component. Para-aortic lymph node, spinal, iliac, and liver metastases were detected along with peritoneal dissemination. Intertrabecular bone metastases were also clinically detected on PET/CT. Abdominal bilateral salpingo-oophorectomy, partial omentectomy, and appendectomy performed for surgical staging revealed the ovarian tumor was primary OSCNEC with peritoneal dissemination because no lung tumor was identified on PET/CT, which ruled out a metastatic ovarian tumor from small cell lung cancer. The patient received radiation therapy for vertebral metastases without chemotherapy and died four months after the operation. OSCNEC could be considered when elevated serum NSE at diagnosis and hematogenic spread such as bone or liver metastases are found in a patient with a primary malignant ovarian tumor without a lung tumor on imaging, although MR findings of OSCNEC were not specific enough to differentiate it from other ovarian cancers.