Rapidly Growing Keratoacanthoma on the Forearm

Keratoacanthoma (KA) is a keratinocytic neoplasm that some experts believe to be a variant of squamous cell carcinoma (SCC). KA is characterized by rapid growth over a few weeks to months followed by spontaneous resolution over 4 to 6 months. If a growth does not resolve, it is thought to be a true SCC.

KA presents as a crateriform papule or nodule with a central, usually keratotic, dell. It sometimes resembles a furuncle or inflamed follicle and is usually pink, red, or purple. KAs range in size from 3 mm to 3 cm. They are sometimes associated with a cutaneous horn and may resemble a giant molluscum, wart, or crusted basal cell carcinoma.

Several rare presentations and expressions of KA have been reported. Ferguson-Smith familial KA consists of large, sometimes ulcerated self-healing lesions. Grzybowski eruptive KAs manifest asthousands of pruritic lesions on the skin and mucosal surfaces; they may produce significant deformity. These conditions may benefit from adjunctive therapy with acitretin or isotretinoin. Subungual KAs can be hard to diagnose because of their atypical appearance. Tissue biopsy is warranted for a rapidly growing subungual lesion.

Treatment options are the same as for SCC. Destruction by electrodesiccation or excision is recommended. KAs are of greatest concern when they occur on the nose and eyelids because they may involute and cause local destruction of tissue that results in permanent scarring and physical impairment.