Gastric Spindle Cell Neoplasm With LMNA::NTRK1 Fusion: A Rare Mimic of Wild-Type GIST

Neurotrophic tyrosine receptor kinase-rearranged spindle cell neoplasms (NTRK-SCNs) are rare mesenchymal tumours defined by oncogenic rearrangements involving NTRK genes. NTRK fusions are exceedingly rare in the gastrointestinal tract and can closely resemble wild-type gastrointestinal stromal tumours (GISTs), posing a diagnostic challenge in the absence of molecular testing. We report a case of a 36-year-old woman with a distal gastric mass initially suspected to be a GIST. Surgical resection revealed a spindle cell tumour with low mitotic activity and perivascular hyalinisation. Immunohistochemistry demonstrated expression of CD34, S100 and pan-TRK and was negative for KIT/CD117 and DOG1. Molecular testing confirmed an LMNA::NTRK1 fusion, consistent with NTRK-SCN. This case highlights the importance of considering NTRK-SCN in KIT/DOG1-negative gastric spindle cell tumours.