Fluorescence in situ hybridization as an ancillary method for the distinction of desmoplastic melanomas from sclerosing melanocytic nevi.

The histopathologic distinction of desmoplastic melanomas from sclerosing (desmoplastic) melanocytic nevi can be difficult, especially when evaluating a partial or superficial biopsy. In the study reported herein, we applied and explored the use of a novel ancillary method, a four-probe fluorescence in situ hybridization (FISH) assay targeting RREB1, MYB, Cep6 and CCND1, to this diagnostic problem. Fifteen sclerosing melanocytic nevi, including desmoplastic Spitz nevi, conventional nevi with prominent stromal sclerosis and sclerotic blue nevi, as well as 15 examples of desmoplastic melanoma, were examined.

Fluorescence in situ hybridization for distinguishing nevoid melanomas from mitotically active nevi.

Nevoid melanoma may resemble benign compound or intradermal nevi by their silhouette and profile on low power. Higher power usually reveals nuclear atypia, confluence of cells, incomplete maturation and dermal mitotic activity. However, to some extent all of these features maybe seen in benign compound or intradermal nevi and no single criteria can be used to differentiate nevoid melanoma from a benign nevus.