Simple melanosis of the bladder: a rare entity.

Simple melanosis of the bladder is an uncommon condition with fewer than 15 reported cases characterized by multifocal, diffuse melanin pigmentation of the urothelial mucosa. It is frequently associated with urinary incontinence or urgency. Histologically, melanin granules are present within urothelial cells or lamina propria macrophages with or without bland-appearing mucosal melanocytes. Although considered a benign entity, the rarity of the lesion warrants regular follow-up cystoscopic evaluation with biopsies to screen for the development of malignancy, especially malignant melanoma. This study presents a "typical" case with light, cytochemical, immunohistochemical, and ultrastructural characterization.