Luminal breast cancers have the most heterogeneous mutations, with Luminal A cancers demonstrating PIK3CA mutations most frequently, followed by Mitogen-Activated Protein Kinase Kinase Kinase 1 (MAP3K1), GATA3, TP53, Cadherin 1 (CDH1), and Mitogen-Activated Protein Kinase Kinase 4 (MAP2K4) alterations, while luminal B cancers have frequent TP53 and PIK3CA mutations (29% each). The gene discussed is MAPK4; the disease is cancer.