Thin melanomas.

Thin melanoma refers to that grouping of melanomas that statistically have a good prognosis and survival rate. A small but significant percentage of these lesions metastasize and cause mortality. Histologically, these lesions comprise a diverse grouping of tumors of any intraepidermal growth pattern; in the radial or vertical growth phase; or in anatomic level I, II, III, or IV. Additional histologic findings may also be variably present, such as regression, tumor infiltrating lymphocytes, and mitoses. Molecular studies suggest that thin melanomas may have different properties to thicker and metastatic melanomas. The factors governing the ability of thin melanomas to metastasize and cause mortality are not known. Certain histologic and molecular parameters, some of which have been alluded to previously, may provide clues to understanding the parameters governing the aggressive nature of some of these lesions. Further research is required to enhance our understanding of thin melanomas.