[Atypical lentiginous nevus: a clinical and histopathologic study of 14 cases]

Atypical lentiginous nevus (of the elderly) is a peculiar form of dysplastic nevus. Clinically, this condition can resemble malignant melanoma and histologically, it has a lentiginous pattern with variable degrees of atypia and an absence of dermal nests. These features may lead to an erroneous diagnosis of lentigo maligna melanoma or lentiginous melanoma.

We reviewed 14 cases of atypical lentiginous nevus diagnosed at the dermatology department of Hospital General de Valencia in Valencia, Spain between December 2007 and March 2009. We studied the clinical and histopathologic features of the lesions after hematoxylin-eosin, Melan-A, and Ki-67 staining and compared our results to data reported in the literature.

Four (28%) of the 14 patients (7 men, 7 women) were under 50 years of age. Clinically, most of the lesions (8/14) resembled atypical nevi and they were all located on the back. Histologically, they all had irregular lentiginous epidermal hyperplasia, with a proliferation of individual melanocytes only in the basal layer of the epidermis and an absence of dermal nests. Focal upward migration of melanocytes into the epidermis was present in just 4 cases. All the lesions had cellular atypia, which was moderate in 85% of cases. The Ki-67 proliferation index was low (<5%) in all the lesions analyzed.

Atypical lentiginous nevi, which can be classified as atypical pigmented lesions with a lentiginous pattern, may clinically and histologically resemble melanoma. Our findings support earlier reports that both clinical and histologic findings may suggest a diagnosis of dysplastic nevus. All of the patients in our series are healthy and free of recurrence after 18 months or longer.