Acanthosis nigricans histological show -

histologically there is marked hyperkeratosis and papillomatosis. Acanthosis nigricans is a brown to black, poorly defined, velvety hyperpigmentation of the skin. It is usually found in body folds, such as the posterior and lateral folds of the neck, the armpits, groin, navel, forehead and other areas signs and symptoms: Acanthosis nigricans may present with thickened, velvety, relatively darker areas of skin on the neck, armpit and in skin folds Pathophysiology: The pathogenesis of acanthosis nigricans is poorly understood, and likely to relate to an interplay of factors, including insulin-mediated activation of ILGF receptors on keratinocytes and increased growth factor levels. Factors involved in the development of acanthosis nigricans include: Increased circulating insulin. This activates keratinocyte ILGF receptors, paicularly IGF-1. At high concentrations, insulin may also displace IGF-1 from IGFBP. Increased circulating IGF may lead to keratinocyte and dermal fibroblast proliferation. Fibroblast growth factor. Hereditary variants are associated with FGFR defects. Increased TGF, which appears to be the mechanism for malignancy-associated acanthosis nigricans. TGF acts on epidermal tissue the EGFR In conjunction with increased end levels of ILGF, it is likely that perspiration and friction may be necessary predeterminants for lesions histology: Mucosal acanthosis nigricans reveals epithelial hyperkeratosis and papillomatosis along with parakeratosis. The epidermis is papillomatous (undulates) and pigmented ("nigricans"). Acanthosis (thickening of the spinous layer) is often not really present, so acanthosis nigricans is often a misnomer in many cases. Ref Harrison 20th edition pg 1217