We report a rare case of primary amelanotic malignant melanoma of the male urethra. A 65-year-old man with a urethral mass was referred to our hospital. A pathological diagnosis of a biopsy specimen revealed malignant melanoma. Thereafter, the patient underwent partial penectomy. The histopathological diagnosis was amelanotic malignant melanoma of the urethra. The patient had received DAV-Feron in an adjuvant setting
however, PET-CT revealed multiple metastasis. After receiving more than 10 cycles of nivolumab, the accumulation of FDG was no longer observed on PET-CT. The patient is currently free from recurrence at 20 months after nivolumab treatment.