A Report of a Rare Case of an Advanced Adult Granulosa Cell Tumor Initially Diagnosed as Primary Ovarian Melanoma

Ovarian granulosa cell tumors are rare gynecological cancers with favorable clinical evolution and survival outcomes. We report a new case of this presentation in a patient that was initially diagnosed as a bilateral primary melanoma of the ovary. The patient is a 51-year-old woman with a history of abdominal swelling and deterioration of her general conditions. Physical examination revealed abdominal distension and diffuse dullness with initially highly elevated cancer antigen 125. Contrast-enhanced thoracoabdominal-pelvic computed tomography showed a left-sided ovarian mass and abundant ascites and pleurisy. Ex-lap surgery found two large bilateral ovarian masses associated with peritoneal carcinomatosis and highly abundant ascites. The histopathological examination of the omental biopsy revealed an undifferentiated tumor proliferation of cells with highly positive Human Melanoma Black 45 marker in favor of an achromic malignant melanoma according to the pathologist. Because of her advanced disease, the patient received a combination of six cycles of neoadjuvant dacarbazine, cisplatin, and paclitaxel and showed partial response based on the response evaluation criteria in solid tumors, followed by total abdominal hysterectomy and bilateral salpingo-oophorectomy with cytoreductive surgery. Unexpectedly, the histopathological analysis of the surgical specimens was in favor of an advanced adult granulosa cell tumor with positive inhibin B. Our patient is alive at her 13(th) month of survival and is being followed by the oncology team. The challenges of the pathological diagnosis of this case are discussed. The diagnosis of primary ovarian melanoma should not be based on one immunohistochemical marker only. A single biopsy of omental implants in peritoneal carcinomatosis during ex-lap surgery should be avoided.