Immune checkpoint inhibitors of CTLA4 and PD-1 for malignant melanoma arising in ovarian cystic teratoma: A case report

RATIONALE: Malignant melanoma (MM) arising in ovarian cystic teratoma (OCT) is a rare disease with poor prognosis. Recently, immune checkpoint inhibitors of cytotoxic T-lymphocyte-associated antigen 4 (CTLA4) and programmed death 1 (PD-1) have shown promising results in MM. Herein we report a case of MM arising in OCT. PATIENT CONCERNS: A 63-year-old Japanese primigravida had lower abdominal pain. Magnetic resonance imaging revealed the presence of an 85-mm mass at the right ovary. DIAGNOSES: The patient underwent right salpingo-oophorectomy for right ovarian tumor, and histopathological examinations revealed MM arising in OCT. On immunohistochemical analysis, the tumor cells were positive for HMB-45, Melan A, and S-100 protein, and negative for programmed death-ligand 1 (PD-L1). BRAF gene mutations were not detected by the Real-Time PCR. Two months after surgery, liver metastasis was detected. INTERVENTIONS: The patient underwent immune checkpoint inhibitors of CTLA4 (ipilimumab) and PD-1 (pembrolizumab and nivolumab). She had interstitial pneumonia associated with ipilimumab, but she safely underwent the immune checkpoint inhibitors therapy along with oral prednisolone. Pembrolizumab, ipilimumab, and nivolumab therapies had poor effect on the tumor. OUTCOMES: Now, the present case has had tumor-bearing survival for 14 months since the initial diagnosis and 12 months since the detection of liver metastasis. LESSONS: This is the first case of MM arising in OCT treated by immune checkpoint inhibitors, with information of PD-L1 immunohistochemical expression and adverse events. The present case is the longest survivor following the detection of recurrence among all the previous reports. The long survival and slow-growing tumor in the present case may be associated with no PD-L1 expressions.