22 January 2009 – Case of the Week #137
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Case of the Week #137
A 72 year old man had a radical prostatectomy for prostatic adenocarcinoma.
What is your diagnosis?
Prostatic adenocarcinoma (Gleason score 3+3 = 6)
Prostatic melanosis is the finding of melanin within prostatic stromal melanocytes and glandular cells. The stromal melanocytes are believed to transfer melanin to the epithelial cells (Am J Clin Pathol 1988;90:530). Prostatic melanosis may be an isolated finding, associated with blue nevus (Eur Urol 1992;22:339) or associated with other prostatic pathology such as adenocarcinoma, as in this case.
The differential diagnosis includes lipofuscin pigment and blue nevus. Although lipofuscin is characteristic of ejaculatory ducts and seminal vesicles, it is also found in prostatic epithelium (Am J Surg Pathol 1994;18:446, Mod Pathol 1996;9:791). It is composed of golden yellow-brown to gray-grown granules (lipofuscin in hepatocytes). It stains with PAS-diastase, Congo Red, Luxol fast blue, Oil red O and Ziehl-Neelsen. Both lipofuscin and melanin stain with Fontana-Masson stain, but lipofuscin is S100 negative.
Blue nevus exhibits spindled stromal cells with marked melanin deposition (cellular blue nevus in skin). Nevus cells without pigment are usually present.
There is no clinical significance to the presence of melanosis in the prostate.
Nat Pernick, M.D., President
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