[Blue nevus of the prostate. Differential diagnosis of prostatic pigmented lesions]

To describe a case of blue nevus of the prostate and propose a more precise terminology in order to avoid the confusion arising from the presence of melanin pigment in the prostatic epithelium and/or stroma.

A 58-year-old patient with adult polycystic kidney is described. The patient demonstrated clinical and radiological findings compatible with benign prostatic hyperplasia and had a PSA of 11.4 ng/ml. After three transrectal biopsies showing no malignancy, the patient underwent transurethral resection. Pathological examination of the specimen disclosed glandular-stromal hyperplasia and extensive melanin pigmentation of stroma or blue nevus of the prostate.

The presence of pigment in the prostate is an extraordinary histological finding that can be ascribed, in most of the cases, to one of the following conditions: a) melanosis or true melanocytosis, in which the melanin pigmentation is produced by the prostatic stromal cells, with or without involvement of the surrounding epithelium (probably in a secondary passive process); b) pseudomelanosis, in which the lipofuscin pigmentation is produced and stored by epithelial cells. In both cases the histopathological findings have no clinical significance or prognostic implications.