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WHO Classification of Tumours


Keratoacanthoma is a dome-shaped, rapidly growing tumour composed of well differentiated squamous cells and represents a neoplastic proliferation of the infundibular epithelium of the hair follicle. Usually solitary nodules with a central keratin plug measuring 1-2 cm in diameter typically grow rapidly over 1-2 months and show spontaneous involution after 3-6 months. In temperate climates, up to 70% of keratoacanthomas affect the face. In subtropical areas, lesions arise also on the arms, the dorsum of the hands, and the lower extremities
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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

Most cases of keratoacanthomas develop in elderly patients, with a male predominance. The tumour occurs more frequently in subtropical areas. The majority of lesions regress spontaneously. Local recurrence and rare cases of metastasis have been reported.