A nodular growth appeared on the wrist of a healthy man (Fig 1) and reached a diameter of 1.5 cm within three weeks. It was hard, red, and shiny with an umbilicated central plug. A small biopsy specimen taken from the edge of this lesion was interpreted as well-differentiated squamous cell carcinoma. Excision of the entire lesion and consideration of the short duration allowed the pathologist to revise his diagnosis to keratoacanthoma. There was no further treatment, and the tumor did not recur.
In another patient a tumor located at the right inner canthus attained the illustrated size (Fig 2) in one month. An initial pathologic diagnosis of cornifying squamous cell carcinoma was questioned when the pathologist was informed of the rapidity of growth. The well-differentiated appearance of the tissue suggested slow growth and was incompatible with the clinical course of the lesion. A diagnosis of keratoacanthoma was made by