Spitz-Type Proliferative Nodule With Novel LMNA-RAF1 Fusion Arising Within a Large Congenital Melanocytic Nevus

Document Type

Conference Proceeding

Publication Date

7-1-2024

Publication Title

Am J Dermatopathol

Keywords

benign melanocytic tumor, case report, clinical article, clonal variation, conference abstract, diagnosis, giant congenital melanocytic nevus, human, human tissue, male, pigmented nevus, preschool child, spitz nevus, spitzoid lesions

Abstract

Congenital melanocytic nevi (CMN) are benign melanocytic neoplasms caused most often by post-zygotic mosaic mutations in NRAS or BRAF.1 Proliferative nodules (PN) may arise within CMNs and show similar rates of NRAS and BRAF mutations, supporting their evolution from a common precursor. Recently, 3 reports have implicated fusion transcripts in RAF1 as the driver of CMNs.2-4 Clonality was confirmed in 2 via sampling of multiple nevi and mosaicism was confirmed in one through absence of the fusion in blood. Preservation of the kinase domain was observed in all 3, suggesting a similar mechanism of MEK activation as its BRAF isoform.5 We previously published on an interesting PN in a ten-year-old boy resembling an angiomatoid spitz tumor; 5 years later, the patient presented with additional PNs with angiomatoid spitz morphology, and sequencing revealed an LMNA-RAF1 fusion. We thus present the fourth case of a RAF1 fusiondriven proliferation in the context of a CMN, further adding to the wide range of its fusion partners and making it worthy of future investigation.

Volume

46

Issue

7

First Page

S30

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