Lentigo maligna and malignant melanoma.

Lentigo maligna, a precancerous lesion, is a brown-black irregularly pigmented freckle, usually occurring on the face of the elderly subject. In a series of 99 patients with malignant melanomas, lentigo maligna was the pre-existing lesion in 21. The clinical and histological findings, and previous publications on the subject are reviewed. Lentigo maligna itself is not a superficial malignant melanoma. After the development of malignant melanoma from lentigo maligna, eight of 21 patients developed metastatic disease. This seems to indicate that once malignant melanoma has developed (whether de novo from the junctional portion of a pre-existing nevus, or from a lentigo maligna), the outlook is the same. During the development of malignant melanoma from lentigo maligna there is an indefinite period when it is virtually impossible to determine histologically whether malignant melanoma is present. Naturally, the inclusion of these indefinite cases will greatly influence reported results of treatment.