Integrating Fluorescence in situ Hybridization and Genomic Array Results into the Diagnostic Workup of Melanoma Association for Molecular Pathology United States and Canadian Academy of Pathology Companion Meeting

Melanoma is the deadliest form of skin cancer. Well-delineated diagnostic histologic criteria for malignancy in melanocytic lesions have been put forth, and are widely accepted. The majority of melanomas can be accurately diagnosed on a sufficient biopsy based on evaluation of these histologic parameters, including asymmetry, lack of circumscription, impaired maturation, hypercellularity, cytologic atypia, dermal mitoses, and pagetoid spread. However, for specific subsets of melanocytic proliferations, there exist conflicting and/or ambiguous features that preclude a definitive consensus diagnosis on histologic grounds (Corona, Mele et al. 1996). These include atypical spitzoid melanocytic proliferations, spindle cell melanomas mimicking atypical fibroxanthomas or other fibrohistiocytic lesions, nevoid melanomas, proliferative nodules versus melanoma in large congenital nevi, melanoma versus clear cell sarcoma, identification of residual melanoma in situ on severely sun damaged skin, melanosis versus regressed melanoma, and melanoma transformation within a dysplastic or other type of atypical nevus. The morphologic limitations in the diagnosis of these histologically borderline melanocytic tumors lead to both under and over diagnosis of melanoma. In fact, misdiagnosis of melanocytic lesions is at the top of the list of malpractice cases in diagnostic pathology (Troxel 2006).