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

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.