Abnormalities in the KMT2D (lysine methyltransferase 2D) gene contribute to the development of various types of cancer, including medulloblastoma, melanoma, lymphomas, leukemia, and cancers of the lung, prostate, kidney, bladder, ovary, pancreas, esophagus, and stomach [62,63,64,65,66,67,68,69,70,71,72,73,74,75,76], disrupting genetic and epigenetic regulation and promoting tumor initiation, progression, and metastasis. The gene discussed is KMT2D; the disease is lung cancer.