Malignant melanoma of the male urethra with increased 5‐S‐cysteinyldopa: A case report

INTRODUCTION: We herein present a case of malignant melanoma of the male urethra with an increased serum 5‐S‐cysteinyldopa concentration. CASE PRESENTATION: A 77‐year‐old man visited our hospital complaining dysuria and a dark brown mass protruding from the external urethral meatus. His serum 5‐S‐cysteinyldopa concentration was elevated beyond the upper limit of the reference range. Biopsy of the tumor was performed, and the histological diagnosis was malignant melanoma. He underwent total penectomy, and the serum 5‐S‐cysteinyldopa concentration was normalized. He remained alive without evidence of locoregional recurrence or distant metastases for 6 months after surgery. CONCLUSION: Malignant melanoma of the male urethra is uncommon. The prognosis is favorable if it is detected in its early stages. This case report suggests that measurement of the serum concentration of 5‐S‐cysteinyldopa, a melanin metabolite, is useful for early diagnosis of male urethral melanoma.