Pigment - an overview

11 Aug.,2022


what are pigments

Blue Nevus, Melanosis, and Prostatic Epithelial Pigment.

Pigmented lesions in the prostate are rare and include blue nevus and melanosis.587,588 In the prostate, the termblue nevus has been used when melanin is confined to the melanocytes in the stroma (Fig. 14A.114), and the termmelanosis has been variably applied for a grossly apparent lesion or microscopically conspicuous melanin pigment found both in the glandular epithelium and within melanocytes and histiocytes in the stroma (Fig. 14A.115).587,589–591 Approximately 50 cases of prostatic blue nevus or melanosis have been reported since the first report by Nigogosyan and colleagues in 1963.592–594 About two-thirds of the pigmented lesions are blue nevi, and the rest are melanosis. A few cases of melanosis associated with prostatic adenocarcinomas have been reported.587,595

The histogenesis of melanin-containing lesions in the prostate is unknown.587,596–602 Most investigators believe that melanin is produced by migrating melanocytes in the stroma, which is then transferred to the glandular epithelium.587,598,602

The age of recorded patients with blue nevus or melanosis ranged from 20 to 80 years (mean 68 years) and the finding was usually incidental, the most common clinical presentation being urinary tract obstruction; the usual clinical diagnosis was BPH. Occasionally, malignant melanoma was suspected intraoperatively because of diffuse dark staining of the prostate. Black to brown discoloration was visible in some lesions on gross examination.587,592,598,600,602–605 Microscopically, pigmented spindle cells with long dendritic processes are found scattered in the stroma, adjacent to the prostatic acini. The cytoplasm of the spindle cells contains finely granular brown or black melanin pigment. The pigment is positive for Fontana-Masson and Lillie ferrous iron stains for melanin. On ultrastructural analysis, the spindle cells contain different stages of melanosomes in white men and only mature-type IV melanosomes in black men.587 So far, only very few primary malignant melanomas of the prostate have been documented.606–609

Lipofuscin pigment in prostatic glandular epithelium has been found in 10% to 100% of prostates by virtue of its positivity for Fontana-Masson, Ziehl-Nielsen, Luxol fast blue, and Oil Red O stains. The chances of finding pigment is greater if the entire gland is examined or if special stains are used for detection. This lipofuscin pigment is present in all zones of the prostate, in normal prostate, and in several pathologic conditions, including high-grade PIN and cancer.64,590 The lipofuscin pigment is usually fine, golden-yellow, either intranuclear or occurring throughout the cytoplasm; it may appear golden-brown or blue. It is finer and less refractile than seminal vesicle lipofuscin pigment. The pigment in the prostate is thought to represent wear and tear and aging pigment because of the accumulation of endogenous by-products within the cell. Awareness of lipofuscin pigment in the prostate is critical, particularly in scant biopsy samples. Glands with nuclear atypia and pigment should not be automatically interpreted as seminal vesicle or ejaculatory duct epithelium, and the possibility of PIN or cancer should be considered as well.