HDAC9 and neoplasm: Based on these hypotheses, we used the “ConsensusClusterPlus” package in R to classify patients with qualitatively different HDAC modification patterns based on the expression of 18 HDAC family genes, and three distinct tumor subtypes were eventually identified using unsupervised clustering (Supplementary Figure S5A), including 317 cases in subtype A, 387 cases in subtype B, and 268 cases in subtype C. We termed these subtypes as HDACsCluster A−C, among which HDACsCluster-C exhibited a prominent survival advantage, whereas HDACsCluster-B had the worst prognosis (Figure 2B).