Primary Neuroendocrine Tumor Arising with a Retroperitoneal Mature Cystic Teratoma in an Adult: A Case Report

Abstract

A 10-cm pelvic tumor was incidentally detected in a 26-year-old woman in screening during pregnancy. Laparoscopy revealed a retroperitoneal tumor, which was suspected to be malignant because a solid lesion was found adjacent to the cystic lesion. She was then referred to our hospital for treatment. Abdominal contrast-enhanced CT and MRI showed a multicystic tumor with an enhanced small nodule at the dorsal side of the tumor that was found in front of the sacrum. Surgical resection was performed and the pathological findings after surgery revealed that the tumor was a retroperitoneal mature cystic teratoma and the small nodule was a neuroendocrine tumor (NET). The clinical course after surgery was unremarkable and the patient was discharged on the 7th day after surgery. Retroperitoneal mature cystic teratomas are relatively rare in adults. Since it has been reported that the frequency of malignant transformation increases with age and the prognosis is poor after this transformation, early surgery is recommended. We report this case as a very rare example of a retroperitoneal mature cystic teratoma containing a NET in an adult, and we include a literature review.