Pigmented Deposits in the Skin.

Pigmented deposits can occur in the skin due to many and varied causes. Some of them are systemic conditions accompanied by involvement of internal organs. Others have serious prognostic implications, and early diagnosis can help in the correct and adequate management of the diseases. In addition, some of them are quite innocuous and the correct diagnosis avoids unnecessary treatments. In this article, we review the morphologic features of some of the most common and some of the less usual pigmented deposits in skin other than tattoos.

Immuno-histochemical evaluation of solar lentigines: The association of KGF/KGFR and other factors with lesion development.

BACKGROUND: Solar lentigines (SLs) are macular hyperpigmented lesions associated with sun exposure and age. Histopathologically, SLs are defined by a hyperpigmented basal layer and elongated rete ridges. The molecular mechanisms involved in the formation and the development of SLs are not completely understood. Our earlier data show that keratinocyte growth factor (KGF) induces hyperpigmentary lesions with histological resemblance to SLs. OBJECTIVE: To investigate the association of KGF/KGF receptor (KGFR) and other pigmentary genes with the progression of SL development. To better understand the possible role of KGF in the pathology of SLs. METHODS: Archived human skin biopsies (24 SLs and 14 healthy skins) were studied using immunohistochemistry for KGF/KGFR, proliferation marker Ki67, stem cell marker keratin-15 (K15), tyrosinase (TYR), stem cell factor (SCF), and protease-activated receptor-2 (PAR-2). RESULTS: An increase in TYR-positive cells and expression was found throughout SL progression, as compared to normal skin. The levels of KGF, KGFR, SCF, Ki67 and PAR-2 varied during SL progression. Ki67, K15 and KGF/KGFR were significantly upregulated at early-mid SL stages. The latest-stage SLs expressed the lowest levels of KGF, KGFR, SCF, Ki67 and PAR-2. CONCLUSIONS: The upregulation of KGF/KGFR might induce the formation of rete ridges and hyperpigmentation. The reduced levels of all examined proteins (except TYR and K15) suggest a possible inactive status (dormancy or quiescence) of advanced lesions.