Adult spinal cord diffuse midline gliomas with piloid features have a better prognosis.

Diffuse midline gliomas of the spinal cord (DMG-SCs) are high-grade, WHO grade 4 gliomas typically associated with a poor prognosis. However, some patients experienced extended survival. We reviewed 43 DMG-SC cases with H3K27M expression and observed that 5 patients with prolonged survival who had Rosenthal fibers and eosinophilic granular bodies in their tumors. These 5 patients (4 males, 1 female, aged 33-64 years, median 53.4) all had thoracic spinal cord tumors. Histologically, the tumors were classified as either low or high-grade gliomas. FAT2 and NF1 were the most common genetic alterations. Notably, these patients had longer preoperative courses and survival times (36 and 25 months, respectively). DNA methylation clustering analysis results show that the five lesions are distributed within the same range. One case is clearly classified as DMG, while others have insufficient calibrated scores. Based on these results, we speculate that DMG-SCs with piloid features may represent a unique subtype with a more favorable prognosis.