Melanosis of the prostate gland: report of a case with neoplastic epithelium involvement.

Prostate gland melanosis is an uncommon lesion and the precise histogenesis is unclear. Melanin may be found within melanocytes in the prostatic stroma, within prostatic epithelium and, rarely, in both locations. The stromal dendritic cell has been shown to contain premelanosomes and melanosomes suggesting primary melanin production by this cell. The melanogenic potential of prostatic epithelial cells has not yet been conclusively established. An example of prostatic melanosis is presented in which stromal and epithelial components were found. This dual distribution of melanin has been regarded as an indication that melanin in the epithelial cells results from phagocytosis of melanin from stromal melanocytes as a secondary phenomenon. Melanin pigment was identified not only within hyperplastic prostatic epithelium but also was found in the epithelial component of a well differentiated prostatic adenocarcinoma.