This review comprehensively examines the multifaceted roles of KMT2C in breast cancer pathogenesis, with a particular emphasis on its interplay with critical oncogenic signalling networks and functional axes, including the IFNγ-EMT/MET axis, the MAPK/ERK and RAS/PI3K/AKT/mTOR pathways, and the KDM6A-MMP3 regulatory circuit. This evidence concerns the gene MMP3 and breast cancer.