Dysregulation, caused by the overexpression, abnormal HDAC recruitment, or loss-of-function mutations of HDACs in human cancer have been detected in solid (neuroblastoma, medulloblastoma, lung, gastric, liver, pancreatic, colorectal, breast, ovarian, prostate, renal, bladder, melanoma, oral, endometrial, pancreatic, thyroid, esophageal) as well as hematological tumors (ALL, CLL, AML, DLBCL, CTCL, HL, Myeloma) [25,26,27]. The gene discussed is HDAC9; the disease is cancer.