Expanding spectrum of "spitzoid" lesions: a small series of 4 cases withMAP2K1mutations

The molecular background of a significant proportion of spitzoid neoplasms is still unknown. Recently, activating mutations inMAP2K1have been described in a few spitzoid lesions, but not in benign Spitz nevi. We report four cases of melanocytic tumors with spitzoid features in which aMAP2K1mutation was detected. The lesions did not show a single distinct phenotype and ranged from benign to malignant. Two cases resembled desmoplastic Spitz nevi. Based on the combination of morphological, immunohistochemical, and molecular findings, one case was classified as benign, one as probably benign, possibly intermediate low-grade (MELTUMP-melanocytic tumor of unknown malignant potential), one case was classified as intermediate (MELTUMP), and one case was considered a superficial spreading melanoma with spitzoid features. Based on this, we conclude thatMAP2K1mutations can indicate a spitzoid genetic signature and can be found in both benign and malignant spitzoid neoplasms.