Plantar Spitz Nevus Resembling Malignant Melanoma: Description of Immunohistochemical Findings

Spitz nevus (SN) is predominantly distributed throughout the lower extremities, while an acral location is rare. Since SN occasionally resembles the clinicopathological presentation of malignant melanoma (MM), it presents a diagnostic challenge, especially on glabrous skin. Past reports suggest that several genetic aberrations are associated with specific clinicopathological subtypes of melanocytic tumors. Immunohistochemistry can provide a clue to the presence or absence of a molecular aberration typical of Spitz tumors. We describe a case of a plantar SN with genetic analysis, including anaplastic lymphoma kinase (ALK), ROS proto-oncogene 1 (ROS1), BRAF (V600E) protein, and BRCA1-associated protein-1 (BAP1). However, we were not able to detect a characteristic gene aberration. To the best of our knowledge, no genetic aberrations in plantar SN cases have been reported. A comprehensive understanding of tumor genomics is expected to play an essential role in the classification of melanocytic tumors. Further genetic research on plantar SN is required to establish new criteria for distinguishing between SN and MM.