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Case Reports

Abstract

Spitz nevi and spitzoid neoplasms are a group of melanocytic lesions that are characterized by larger-sized melanocytes with epithelioid and/or spindled morphology. They exist on a spectrum of benign to malignant, the latter termed Spitz melanoma, with indeterminate lesions referred to as atypical Spitz melanocytoma. Herein we describe a case report of a 12-year old male child who was initially diagnosed with invasive melanoma of the left forearm. The review of outside slides demonstrated an ulcerated lesion comprised of predominantly spindled melanocytes with fibrillar cytoplasm and enlarged nuclei, arranged as elongated and fusiform fascicles. There was foci of increased mitotic activity. An ALK (D5F3) immunostain was positive. Molecular studies performed in parallel using NYU FusionSEQer custom solid tumor panel revealed an MLPH (NM_024101.6: exon 14): ALK (NM_004304.4:exon:20) fusion in 60% of the lesional cells. Additional methylation analysis identified no unbalanced copy number (CN) losses or gains. Methylation classified the lesion with melanotic schwannoma. Given these findings and the fact that MLPH:ALK fusion can be seen in pediatric Spitz nevi, which may exhibit plexiform growth pattern and infiltrative borders, a diagnosis of a traumatized ALK positive Spitz nevus was rendered. A diagnosis of challenging spitzoid and spitz lesions can be assisted by both RNA and methylation analysis. In addition to accurately classifying the proliferation, methylation enables identification of CN across the genome and presents a potential to be used when SNP array data is unavailable.