The normal skin is lined by epidermis , dermis & subcutis other appendages. Skin appendages develops from ectoderm during early embryonic life. These specialized structures are located deep within the dermis & in subcutis. Includes pilo-sebaceous units( hair follicles & sebaceous glands), eccrine & apocrine glands. Hair follicle show invagination from epidermis. Hair bulb is highly vascular part and is seen in reticular dermis. The inner mitotically active cells lines the dermal papillae undergo keratinization- hair shaft and inner root sheath. Each hair shaft consists of an innermost medulla, surrounded by highly keratinized cortical layer, and an outermost thin layer - cuticle. The outer 2 layers of hair bulb form the outer root sheath, containing glycogen-rich (clear) cells and is separated from the dermal connective tissue by a thick glassy membrane. Adnexal tumor is a benign or malignant lesion with the differentiations . The lesions may be single or multiple. Some tumors may be associated with syndromes (familial or sporadic). Malignant lesions are rare, locally aggressive ,shows nodal involvement & distant metastasis. The tumours are divided based on the follicular differentiation into benign, malignant and hyperplastic lesions. The benign neoplasms are Trichoblastoma, Pilomatricoma, Trichilemmoma, Trichofolliculoma, Fibrofolliculoma. The malignant lesions are Pilomatriceal carcinoma and proliferating trichillemal tumours. The various types of the differentiations includes, hair germ, infundibular, outer root sheet, matricel, follicular and mesenchymal. There are several syndromes associated with the pilar origin tumours with the gene abnormalities.
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