After getting DEGs in tumor tissues compared with normal tissues, network-based analyses (such as protein–protein interaction networks of the DEGs) verified that CCNA2 is a hub gene in LIHC (Li et al., 2021a), LUAD (Zeng et al., 2020), LUSC (Gao et al., 2020), STAD (Ji et al., 2021), PRAD (Feng et al., 2021), HNSC (Zhang et al., 2020), THCA (Li et al., 2020b), medulloblastoma (Guo et al., 2020a), mantle cell lymphoma (Guo et al., 2020b), and colorectal cancer (Wang et al., 2020). The gene discussed is CCNA2; the disease is mantle cell lymphoma.