We evaluated the immunohistochemical expression of p16, and the presence of CDKN2A genetic alterations detected through fluorescence in situ hybridization (FISH) and multiplex ligation-dependent probe amplification (MLPA), in a series of 130 Spitz nevi, 20 atypical spitzoid tumors, and 11 spitzoid melanoma.
This case demonstrates the presence of clonal heterogeneity of losses of chromosome 9 and p16 protein expression within a single spitzoid melanoma, challenging a robust application of p16 expression detected only by immunohistochemical staining in determining the diagnosis of spitzoid melanoma.