Key result
Molecular analysis identifies rare PDGFD-rearranged dermatofibrosarcoma protuberans mimicking an NTRK-rearranged spindle cell tumor.
Case Report (n=1)
Dermatofibrosarcoma protuberans should be considered in tumors with focal S100 expression, as alternative PDGFD rearrangements can occur.
IHC pan-TRK/S100 positivity risks misclassifying PDGFD-rearranged DFSP; molecular testing extends the fusion spectrum and is required for accurate diagnosis.
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.
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Podesta et al. (2026) conducted a case report in Dermatofibrosarcoma protuberans (n=1). PDGFD rearrangement was evaluated on Tumor diagnosis and molecular characteristics. A rare case of PDGFD-rearranged dermatofibrosarcoma protuberans with focal S100 and pan-TRK expression was identified, mimicking an NTRK-rearranged spindle cell tumor.
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