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WHO Classification of Tumours


Tricholemmoma (TL) is a benign cutaneous proliferation arising predominantly on the face. It usually presents as a small (3-8mm), solitary exophytic lesion which is either verrucous and keratotic or dome-shaped with a smooth surface. Histologically, TL presents as a sharply circumscribed, bulbous infundibular hyperplasia with tricholemmal differentiation. The infundibula show marked para- and hyperkeratosis and hypergranulosis and are surrounded by a collarette of adnexal epithelium. The tumour lobules consist of pale and clear isomorphic epithelial cells and are in continuity with the epidermis. The interfollicular epidermis is not involved. At the tumour periphery, there is a palisade of pale columnar cells, bordered by a prominent basement membrane.
Tricholemmoma occurs predominantly in adults. It is an entirely benign tumour; however, multiple TLs are frequently associated with Cowden disease , a search for internal malignancy is therefore indicated in these cases

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LeBoit PE, Burg G, Weedon D, Sarasin A (Eds.)
World Health Organization Classification of Tumours. Pathology and Genetics of Skin Tumours
3rd Edition
IARC Press: Lyon 2005


In the vulva, tricholemmoma is rare. The tumour presents as a slow-growing solid mass with a dermal pushing border that may show no connection with the overlying epithelium

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Avinoach I, Zirkin HJ, Glezerman M (1989)
Proliferating trichilemmal tumor of the vulva. Case report and review of the literature.
Int J Gynecol Pathol 8: 163-8

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Tavassoli FA, Devilee P (Eds.)
World Health Organization Classification of Tumours. Pathology and Genetics of Tumours of the Breast and Female Genital Organs.
3rd Edition
IARC Press: Lyon 2003