Expanding the Spectrum of the Soft Tissue Tumors with Kinase Gene Fusions: A Pediatric Spindle Cell Neoplasm Harboring MTAP-RAF1 Fusion.

Introduction: NTRK-rearranged spindled cell tumors have been increasingly recognized with the widespread use of molecular studies. We describe a pediatric spindle cell neoplasm with MTAP-RAF1 gene fusion that fits into this group. Case report: An 8-year-old girl presented with mandibular mass. Histopathologically, it was a moderate to increased cellular spindle cell tumor with mild-to-moderate nuclear pleomorphism, focal perivascular keloid-like collagen, that was positive for S-100 and CD34. MTAP-RAF1 fusion was detected by next generation sequencing, confirming a low-grade sarcoma with MTAP-RAF1 fusion that is presently included in the category of NTRK-rearranged spindled cell tumors. Discussion: MTAP-RAF1 fusion, in the spectrum of spindle cell neoplasms with kinase gene rearrangements, can occur in the pediatric age group.