TRAF7-Mutated Myxoid and Spindle Cell Mesenchymal Tumor Occurring in a Pediatric Patient in the Post-Transplant Setting: Expanding the Spectrum of TRAF7-Mutated Tumors.

TRAF7 mutations have been reported in many tumor types, including subsets of meningiomas, mesothelioma, intraneural perineuriomas, and rare cases of aggressive fibromyxoid spindle cell tumors in adults. We expand the spectrum of TRAF7-mutated tumors by reporting a case of a TRAF7-mutated myxoid and spindle cell mesenchymal tumor in a 13-year-old female with a history of a heart and renal transplant. Histopathologic examination demonstrated hypocellular areas composed of bland spindle cells in a myxoid matrix and hypercellular areas with significant pleomorphism and up to 13 mitotic figures per 10 high-power fields. The spindle cells were positive for CD34 and negative for smooth muscle actin (SMA) and S100. Whole exome sequencing identified a TRAF7 p.S561R mutation. Methylation profiling illustrated that the tumor did not embed within a distinct tumor group. The tumor was resected, and the patient remains stable at 7 months follow-up. This report is the first known case of a TRAF7-mutated myxoid and spindle cell tumor in a pediatric patient.