Aggressive amelanotic lentigo maligna.

A 66-year-old woman had a long-standing, scaly erythematous lesion on her left temple which histologically showed features of amelanotic lentigo maligna. It had recurred on numerous occasions over a period of 17 years, in spite of multiple attempts at curative surgery. There were also recurrences within a skin graft which, to our knowledge, has not been documented previously with lentigo maligna. In spite of the prolonged course, and extensive intraepidermal melanocytic proliferation amounting to melanoma in situ, there has been no evidence of dermal invasion. The lack of pigmentation in such lesions means that clinical definition of margins is highly inaccurate. In view of the aggressive horizontal growth phase of this lesion, with rapid recurrence following surgery, it was treated with electron beam therapy, and this has resulted in complete clinical remission. This most unusual case illustrates the potential difficulties in diagnosis and management of amelanotic lentigo maligna.