Diffuse astrocytoma, MYB/MYBL1 altered, shows amplifications and variants of MYB or MYBL1, with fusion involving partner genes like PCDHGA1, MMP16, and MAMAL2. MYB is a proto-oncogene involved in the proliferation and differentiation of cells. The gene discussed is MYB; the disease is astrocytoma (excluding glioblastoma).