Objectives Melanoma accounts for 3% of skin neoplasms in Brazil, with an incidence of 1.7% in women in the year 2018, according to the National Institute of Cancer. It can appear in any part of the body, but the skin is the primary site in 90% of cases. In 2–3% of the cases, the primary site is unknown. In this context, the objective is to present a rare case of ovary metastatic melanoma.

Methods We present a case report of a 36-year-old patient who underwent bilateral oophoroplasty and tubo-ovarian abscess drainage due to an acute inflammatory abdomen. Initially anatomopathological results of ovary dysgerminoma showed a 11 cm tumor with approximately 10% tumor necrosis and index mitotic 6/10. Histopathology study showed a superficial spreading melanoma, while immunohistochemistry discrimination was positive for S100, HMB-45, and Melan-A.

Results The case evolved with right inguinal lesion and bilateral adnexal tumors. Positron emission tomography showed multiple peritoneal implants, metastatic lesions in the lumen of the gastric body, peritoneal implants, and abdominopelvic lymph node enlargement. Biopsy of right inguinal lymph node and stomach biopsy returned positive for metastatic melanoma. The patient is currently being treated with immunotherapy.

Conclusions The cutaneous melanoma dissemination to the gynecological tract is rare. The prognosis depends on the initial state and in advanced stages the prognosis declines, mainly due to the high rate of metastases, which are mostly lymphatic. Our case report demonstrates a diagnosis of ovarian malignant melanoma which simulated primary ovarian cancer. The differential diagnoses are sex cord-stromal tumors and germ cell tumors.