Vaginal malignant melanoma is a rare and aggressive tumor, and the standard treatment has not been established. Recently, immune checkpoint inhibitors via PD-1 and CTLA-4 have caused breakthroughs of standard therapy for cutaneous malignant melanoma. However, there are still limited reports of immune checkpoint inhibitors for vaginal malignant melanoma.

50-years-old woman, G1P1. She visited our hospital to evaluate abnormal genital bleeding for several months and vaginal tumors. Her pelvic examination and pelvic MRI showed a 4 cm blackish, polypoid tumor in the vagina. Histological examination of biopsy diagnosed malignant melanoma. Contrast-enhanced CT showed pelvic lymph node metastasis. Finally, she was diagnosed with vaginal malignant melanoma, cT1N1M0. The BRAF gene was wild type. She started ipilimumab (3 mg/kg, tri-weekly) plus nivolumab (1 mg/kg, tri-weekly) combination therapy. At the end of the 3rd course, autoimmune hepatitis (grade 4) and thyroiditis were observed. They were considered immune-related adverse events. Intravenous methylprednisolone pulse and Mycophenolate Mofetil slowly improved liver function. The 4 cm-sized vaginal tumor shrank to under 1 cm, and the enlarged lymph nodes disappeared. Currently, we are considering surgical intervention and/or maintenance chemotherapy with nivolumab alone.

We experienced a combination therapy of ipilimumab + nivolumab for vaginal malignant melanoma. While the combination therapy was highly effective, severe immune-related adverse events were observed. There are also reports that cases with immune-related adverse events have a high response rate. It was considered necessary to accumulate experience of immune checkpoint inhibitors for vaginal malignant melanoma in the future.