Abstract
Primary melanoma of male urethra is exceedingly rare. The diversity in morphology, especially in nontraditional locations, can make the diagnosis of melanoma uniquely challenging. We describe the case of a 53 year-old healthy man who presented with 3 months of gross hematuria. Initial CT abdomen/pelvis scan was unremarkable. He underwent cystoscopy with bladder and urethral biopsies outside our hospital with preliminary histopathologic description of invasive high-grade tumor with pleomorphic atypical nuclei suggestive of poorly differentiated urothelial carcinoma. This patients care was transferred to our institution. The patient underwent re-biopsy with urine cytology. Outside slides were re-read and the new biopsy results showed poorly differentiated tumor cells with plasmacytoid features that turned out to be negative for all urothelial markers (GATA3, uroplakin, p63). The initial differential diagnosis included metastasis, plasmacytoma, and lymphoma with secondary differentials of epitheliod sarcoma and melanoma. An immunohistochemical workup showed that the tumor retained INI-1 and was negative for cytokeratins, CD45, CD20, CD3, CD138, NKX3.1. Detection of pigmented cells on the biopsies and cytology prompted work up of Melan-A and HMB-45 that were strongly positive. The final histopathology diagnosis was melanoma of the distal urethra. PET CT scan confirmed an abnormal hypermetabolic area at the distal urethra. Dermatology consult was negative for melanoma. The patient underwent cystoprostatectomy with urethrectomy which later confirmed the diagnosis of primary melanoma of distal urethra. This case represents a potential pitfall in diagnosing primary urethral melanoma in males as poorly differentiated urothelial carcinoma because of low prevalence and high mimicry of this entity.
Financial Disclosure:
No current or relevant financial relationships exist.
