Eruptive squamous cell carcinomas, keratoacanthoma type, arising in a multicolor tattoo.

Permanent tattoos are formed through the injection of ink solids through the epidermis into the dermis and can cause multiple adverse reactions. We report a 38-year-old man who presented to our Dermatologic Surgery Unit with a diagnosis of a superficially invasive squamous cell carcinoma (SCC), keratoacanthoma (KA) type, of the left forearm in a 1-month-old tattoo. Since his initial biopsy, he developed four more similar lesions on his left forearm within his tattoo. On physical examination, the patient had a large, multicolor tattoo on his left forearm, a well-healed surgical biopsy site and four erythematous hyperkeratotic papules within differently pigmented areas of the patient's tattoo. Histopathological examination showed KA and tattoo pigment. Based on the eruptive nature of these lesions, their clinical presentation and the histopathological changes, we report this as the first case of eruptive KA arising in a multicolor tattoo.