Clinicopathological and molecular characteristics of adult cerebellar malignant gliomas: a 25-year single-center experience

Introduction Cerebellar malignant glioma is an extremely rare tumor, and its clinicopathological and molecular features remain unclear. Methods The clinical course, radiological findings, histopathology, and molecular characteristics of 11 adult patients (23–83 years; median: 75 years) with cerebellar malignant glioma who were treated between 2000 and 2024 were reviewed. Results The primary site of the lesions was the cerebellar vermis in 4, cerebellar hemispheres in 5, and cerebellopontine angle in 2 patients. Perifocal edema was obscure in all but 2 patients. Considering the clinical information, and neuroimaging characteristics, the initial preoperative differential diagnoses were metastatic brain tumor in 3, malignant glioma in 3, ependymoma in 2, and malignant lymphoma, schwannoma, and pilocytic astrocytoma in 1 patient each. Ten patients underwent excision surgery, and 1 patient underwent biopsy. In the 2 patients in whom malignant glioma was strongly suspected before surgery, photodynamic therapy was performed intraoperatively. Initial pathological analysis showed that 8 patients had grade 4 glioma, and 3 patients had grade 2/3 glioma. The patient with grade 3 astrocytoma subsequently experienced recurrence with histological progression to grade 4. Isocitrate dehydrogenase 1 was wildtype in all 7 tested patients. The tumor tissues demonstrated heterogeneous histopathological features, including oligodendroglial, pilocytic, and giant cell-like components, in addition to the typical characteristics of glioblastoma. Notably, cerebellar infiltration of tumor cells was also observed. The tumors of 4 patients also had piloid features, and required differentiation between glioblastoma and high-grade glioma with piloid features (HGAP). Of the 9 patients who experienced recurrence, 4 demonstrated local recurrence, whereas the other 5 demonstrated distant or disseminated recurrence. The median overall survival was 29.0 months for all patients, and 19.5 months when limited to patients with grade 4 glioma including the patient with histological progression. Conclusion Cerebellar malignant gliomas demonstrate considerable heterogeneity regarding their imaging, histopathology, and molecular profiles. Accurate diagnosis often requires integrated molecular analyses, including DNA methylation profiling. The identification of rare variants, such as HGAP, is essential for the appropriate diagnosis and management of cerebellar malignant gliomas.