ABSTRACT
Melanin pigment may be found within stromal cells or in the epithelial lining of acini or ducts. Melanin-containing stromal cells may give rise to the rare blue nevus of the prostate. The presence of melanin pigment within prostatic epithelium is designated as prostatic epithelial melanosis. The urologic surgeon and the pathologist must be cognizant of this lesion that grossly simulates a malignant melanoma. Blue nevus of the prostate is a tumor of dendritic melanocytes which may be found in the fibromuscular stroma. Ultrastructural examination revealed large number of melanosomes within the dendritic melanocytes. In the blue nevus of the prostate of a 76-year-old white man, melanosomes in various stages of development were present in the melanocytes. Epithelial melanosis may or may not be associated with the presence of stromal melanocytes. Epithelial melanosis is considerably more common than blue nevus of the prostate.
