Rare melanosis in the urinary bladder and prostate: a case report

Melanosis, the aberrant deposition of melanin pigment in the absence of melanocytes, is very rare in the genitourinary tract. We report a case of a 74-year-old male with symptomatic benign prostatic hyperplasia. Diagnostic cystourethroscopy demonstrated bladder mucosa remarkable for numerous flat, velvety, and brown-black lesions. The patient underwent cystolitholapaxy, transurethral resection of the prostate, and bladder biopsy. Microscopic examination of the bladder biopsy demonstrated urothelium with granular, black pigmentation within the mucosa and histiocytes in the lamina propria; a Fontana Masson stain was positive for melanin. Microscopic examination of the transurethral resection of the prostate demonstrated nodular hyperplasia with focal, black pigmentation of the stroma. The rarity of bladder and prostate melanosis highlights the need for further investigation to elucidate its clinical significance and provide assurance of its benignity. Despite its rarity, melanosis should be kept in the differential diagnosis when melanotic lesions are encountered during cystoscopy.