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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.

American Journal of Dermatopathology: October 1996 - Volume 18 - Issue 5 - pp 543-547
Extraordinary Case Reports

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.

From the Departments of Pathology (E.P., R.G.) and Dermatology (J.J-R., C.G-H.), Hospital Universitario de Getafe, Madrid, Spain.

Address correspondence and reprint requests to Dr. R. Granados, Departamento de Anatomia Patologica, Hospital Universitario de Getafe, Carretera de Toledo, Km. 12,500, Madrid, Spain.

© Lippincott-Raven Publishers