Blue nevus of the prostate.

Blue nevus is one of the melanotic lesions that can incidentally arise in the prostate gland. A literature review identified 28 previously reported cases, and although rare, the blue nevus appeared to be the commonest melanocytic lesion arising in the prostate. The differential diagnosis includes melanosis and malignant melanoma, as well as nonmelanotic lesions due to deposition of lipofuscin, hemosiderin and, rarely, homogentisic acid. The distinction among these lesions can typically be made based on morphologic grounds but may also be aided by histochemical and immunohistochemical stains such as stains for iron, S100 protein, HMB-45, and CD68 as needed. Blue nevus of the prostate is a benign lesion with no malignant potential to date, so no further treatment is warranted.