Cutaneous Juvenile Xanthogranuloma With MRC1::PDGFRB Gene Fusion: A Case Report.

Juvenile xanthogranulomas (JXGs) are benign solitary or multiple lesions that present as yellow-red nodules on the skin or other organs, with histology demonstrating normolipidemic, non-Langerhans cell histiocytosis. We present a case of a clinically atypical lesion shown to be of the JXG family of lesions following pathologic review. Next-generation sequencing (NGS) analysis revealed a MRC1::PDGFRB gene fusion. This is the third report of the MRC1::PDGFRB gene fusion identified in JXG, and the first case of an isolated cutaneous lesion, which highlights the spectrum of the MRC1::PDGFRB gene fusion in JXG.