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American Journal of Dermatopathology:
Extraordinary Case Reports

Trichilemmal Keratosis: A Clinicopathologic and Immunohistochemical Study of Two Cases

Poblet, Enrique M.D.; Jimenez-Reyes, Jose M.D.; Gonzalez-Herrada, Carlos M.D.; Granados, Rosario M.D.

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Trichilemmal keratosis (TK) is an uncommon epidermal tumor that exhibits a keratinizing surface with the formation of a cutaneous horn and that clinically resembles a hyperkeratotic actinic keratosis. Histologically, there is verrucous hyperplasia of the epidermis with orthokeratotic hyperkeratosis. TK is characterized by abrupt keratinization without formation of a granular cell layer, in the same manner as that in which the outer root sheath keratinizes (trichilemmal keratinization). The epidermis is acanthotic and contains pale-staining keratinocytes. Epithelial lobules and small trichilemmal cysts are connected to the thickened epidermis. We describe the clinical, histologic, and immunohistochemical findings of two cases of TK.

© Lippincott-Raven Publishers


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