While some chromosomal changes (e.g., chromosomes 1, 10, 17, and 22) and genetic mutations (e.g., MMP25, MMP9, NFKBIA, and DMBT1) are characteristic of several types of brain tumors, detecting changes specific to certain tumors (e.g., the formation of isochromosome 17q in medulloblastoma) is crucial for prognosis and therapy effectiveness. The gene discussed is MMP9; the disease is medulloblastoma.