Specific alterations involving MAPK genes (MAP3K8 fusions, MAP3K3 fusions) have been recently detected in a subgroup of spitzoid neoplasms that seem to constitute a distinctive clinicopathologic group, occur mostly in younger patients (median age 18 years) and present with atypical histologic features associated with frequent homozygous deletion of CDKN2A, qualifying a high proportion of them as Spitz melanoma (malignant Spitz tumor). Apart from lesions with spitzoid morphology harboring MAP3K8 or MAP3K3 fusion, a single case with MAP2K1 deletion has been identified. The authors report herein 4 melanocytic lesions with a MAP2K1 mutation, all showing similar microscopic appearances, including spitzoid cytology and dysplastic architectural features, resembling so-called SPARK nevus, suggesting that these lesions may represent another distinctive group.

Bioptical Laboratory Pilsen Czech Republic

Department of Clinical Genetics Umeå University Umeå Sweden

Department of Pathology NEMOS Hospital Sokolov Czech Republic

Department of Pathology Regional Hospital Ceske Budojovice Czech Republic

Department of Pathology Regional Hospital Kladno Czech Republic; and

Department of Pathology Umeå University Umeå Sweden

Department of Pathology University Hospital Campus Bio Medico Rome Italy

Sikl's Department of Pathology Medical Faculty in Pilsen Charles University Prague Pilsen Czech Republic

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