[Genetic alterations in the differential diagnosis of melanocytic diseases]

The biological significance of melanocytic lesions depends on its association with melanomas. Some melanocytic lesions are considered as precursors of melanoma while others may share histological similarities with malignant lesions. Melanomas exhibit clinical, epidemiological and histological heterogeneity. Molecular and cytogenetic studies may supply additional information to supplement the histopathological evaluation. Several genes have been linked to melanomas: CMM1 on chromosome 1p36 and CMM2 on 9p21, and other chromosomal regions where tumor suppressor genes are located as p16 (9p21) and p53 (17p13). We analyzed different melanocytic lesions to determine LOH at 9p21 and 17p13 and to assess clonality by the HUMARA technique. All the malignant melanomas were monoclonal and all the benignant lesions we analyzed were policlonal in our series including deep penetrating nevi and Spitz Nevi. LOH at 9p21 was determined in 60% melanomas, 50% Spitz and 0% intradermal nevi. In conclusion, genotypic changes may supplement the phenotypic or morphological evaluation of melanocytic lesions.