Squamous cell carcinoma arising in a linear epidermal nevus.

An isolated, pruritic lesion developed in the right breast of a 17-year-old girl during a period of four months. The lesion was well circumscribed, erythematous, indurated, and markedly hyperkeratotic in the center. The histologic diagnosis was well-differentiated squamous cell carcinoma arising in a linear epidermal nevus. The development of squamous cell carcinoma in a linear epidermal nevus is a rare event, previously reported only in long-standing, extensive lesions of middle-aged to elderly patients. This case seems to be unique in regard to the patient's young age, the short duration of the nevus, and the lack of identifiable predisposing factors.