Track

Case Reports

Abstract

Dermatofibrosarcoma protuberans (DFSP), the most common cutaneous sarcoma, is characterized by a specific translocation t(17;22)(q22;q13) leading to the formation of COL1A1::PDGFB fusion transcripts. Approximately 4% of DFSP cases remain negative for this fusion in routine molecular screening. This prompted the investigation and discovery of other rearrangements, such as COL6A3::PDGFD, COL1A2::PDGFD, EMILIN2::PDGFD, SLC2A5::BTBD, and CSPG2::PTK2B. Here, we report a case of DFSP with a novel fusion.

A 21-year-old woman presented with a 1.0 cm, movable, tender lesion on her left proximal forearm that had been enlarging and was clinically suspected to be a lipoma. Histologic sections demonstrated multiple fragments of a hypercellular neoplasm composed of uniform spindled cells arranged in storiform pattern. Tumor cells demonstrated pale eosinophilic cytoplasm, vesicular chromatin, and inconspicuous nucleoli.  Significant cytologic atypia or necrosis was not identified, and no fibrosarcomatous areas were present. Further characterization of the lesion through immunohistochemical stains showed diffuse positivity for CD34 and negativity for STAT-6 and SOX10 in the neoplastic cells, with focal nonspecific staining for S100. To further classify this lesion, next-generation sequencing was performed. An EMILIN1::PDGFD fusion was detected.

To the best of our knowledge, this EMILIN1::PDGFD fusion has not been described in the English literature. Whether certain fusions increase the risk of fibrosarcomatous transformation, and thereby lead to more aggressive course, is still unclear. Awareness of these variants is crucial for dermatopathologists, as they may not be detected using conventional reverse transcription polymerase chain reaction (RT-PCR)- or fluorescence in situ hybridization (FISH)-based diagnostic assays for DFSP.