Actas del 8º CVHAP, Seminarios de Casos

Prostate melanosis associated with acinar adenocarcinoma.

Clóvis Klock, Regina Paula Xavier Gomes, Michel Adriano Thomé João, Ivan Tadeu Rebouças


The prostate contains two different types of pigments: lipofucsin and melanin. Lipofuscin is found in the benign prostate epithelium, as well as in advanced intraepithelial prostatic neoplasias and prostatic adenocarcinomas. Melanin is rarely found, except for melanocytic lesions such as the blue nevus, melanosis and malign melanomas. Prostatic melanosis is an extremely rare event with only 20 cases reported so far. Here we present a case where the melanic pigment was found in the stroma, the normal epithelium and associated to the neoplastic epithelium of the prostatic acinar adenocarcinoma. Patient A.S., caucasian, 85 y.o. PSA = 79 ng/ml (values up to 10 ng/ml are considered normal). The patient was submitted to transurethral resection of the prostate (yielding several fragments adding up to 7.0 g) and bilateral orchiectomy. Microscopic analysis showed infiltrative glandular lesion with acinar fusion (Gleason pattern 7 = 4+3). Moreover, dark granules were observed in fibromuscular cells of the stroma of both the prostatic epithelium and neoplastic acini. The granules were negative for the iron – Prussian blue reaction and positive for the Fontana – Masson staining, indicating a melanic nature. These melanin-containing stroma cells are long with smooth edges. The testicles presented no noticeable feature and both showed normal spermatogenesis. Immunohistochemistry analysis using an anti-PSA monoclonal antibody (Dako. Clone ER-PR8. 5/300 dilution) positively stained the usual stroma and epithelial neoplastic cells. Benign melanocytic proliferations are a rare event and their association with adenocarcinoma is even more so. The origin of the melanocytes found in the prostate is uncertain, though it probably results from a joint migration with the mesoderm. The presence of melanin in the epithelium probably depends on the transmission from stromal melanocytes and although rare, malignization of the stromal component should be discarded.

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