This revised 2021 WHO CNS5 tumor classification system marked a paradigm shift by fully integrating molecular features into glioma classification and grading, combining traditional histopathological evaluation with key molecular markers (e.g., IDH mutation status, 1p/19q codeletion, CDKN2A/B deletions, and histone mutations) to more accurately reflect the biological prognosis, and predictive therapeutic implications of these tumors (1) (Table 1). The gene discussed is CDKN2A; the disease is neoplasm.