A High-Grade CD34-Positive Spindle Cell Sarcoma of the Palm Revealing an Unexpected TPM3::NTRK1 Fusion: A Diagnostic Pitfall With Major Therapeutic Implications.
Ayoub Nahal, Mahmoud El Kaissi, Suzan A Mbaideen et al.
✦ AI-curated · Sources linked
Case in brief
A 17-year-old male presented with a rapidly enlarging palmar mass that recurred locally after excision. The tumor was first diagnosed as synovial sarcoma and later reinterpreted as fibrosarcomatous dermatofibrosarcoma protuberans. Despite multiagent chemotherapy intended to preserve the limb, it progressed, requiring midforearm amputation. Expert review of the amputation specimen found diffuse cytoplasmic pan-TRK staining; next-generation sequencing confirmed a TPM3::NTRK1 fusion, establishing an NTRK-rearranged spindle cell sarcoma.
What made this case unusual
The high-grade CD34-positive spindle cell tumor was successively classified as two different sarcoma types before pan-TRK staining and sequencing revealed the TPM3::NTRK1 fusion.
Diagnostic / clinical pearl
In high-grade CD34-positive spindle cell sarcomas, consider an NTRK-rearranged neoplasm and incorporate pan-TRK immunohistochemistry early, with molecular confirmation when indicated.
Why it matters
Identifying the fusion can establish eligibility for TRK-inhibitor therapy, a treatment implication that was missed during this patient’s initial diagnostic work-up.