KMT2D and metastatic malignant neoplasm in the lymph nodes: Other important clinical information of MM, such as the Clark level, Breslow thickness, lymph node metastasis, distant metastases, which unfortunately were not recorded for most patients in our study, need to be tested in future studies to further clarify the clinical roles of KMT2D. KMT2D is a histone methyltransferase that primarily performs monomethylation on the lysine 4 position of histone H3 (H3K4me1).