dermatologic disorders
Keratoacanthoma
Introduction
Keratoacanthomas are round, firm, usually flesh-colored nodules with sharply sloping borders and a characteristic central crater containing keratinous material; they usually resolve spontaneously, but some may be a well-differentiated form of squamous cell carcinoma. Diagnosis is by biopsy or excision. Treatment is with surgery or injections ofmethotrexateor 5-fluorouracil. (See also Overview of Skin Cancer .) Etiology of keratoacanthoma is unknown. Most experts consider these lesions to be well-differentiated Squamous Cell Carcinoma with a tendency to involute. Development is rapid. Usually the lesion reaches its full size, typically 1 to 3 cm but sometimes>5 cm, within 1 or 2 months. Common sites are sun-exposed areas, the face, the forearms, and the dorsum of the hands. Spontaneous involution may start within a few months, but involution is not guaranteed. 