PDGFD ‐Rearranged Dermatofibrosarcoma Protuberans With S100 and Pan‐ TRK Expression

ABSTRACT

Dermatofibrosarcoma protuberans (DFSP) is a fibroblastic malignancy characterized in most cases by COL1A1::PDGFB fusion. Rare cases exhibit alternative rearrangements involving PDGFD . Here, we describe a female patient in her third decade of life who presented with a spindle cell proliferation on the shoulder. Expression of pan‐TRK and S100, together with absence of PDGFB overexpression, supported an initial impression of NTRK ‐rearranged spindle cell tumor. However, molecular analysis revealed PDGFD rearrangement, and re‐excision demonstrated classic DFSP morphology in the residual tumor. Our findings underscore the importance of continued consideration for DFSP in tumors with focal S100 expression.