Lentigo maligna.

Lentigo maligna (LM), a melanoma in situ, is a fairly common melanocytic lesion that usually develops on the chronically sun-exposed skin of the head and neck of Caucasians. It occurs mostly in people older than 40 years, with an incidence rate that increases with age and peaks in the seventh and eighth decades of life. Its diagnosis and treatment remain challenging. In this article, we review the history, epidemiology, clinical presentation, histology, and treatment of LM.