CA XII mRNA is overexpressed in the HCC cohort from the TCGA and GEO databases. The mRNA levels of CA XII in HCC samples and normal counterpart tissues were compared in a cohort of patients from the TCGA (A, P = 0.000). CA XII expression in the groups stratified by sex (B, P = 0.010) and tumor pathologic grade (C, P = 0.028). CA XII mRNA expression in HCC is significantly elevated compared with that in normal tissues, as observed in the microarrays GSE39791 (D, P = 0.000), GSE63898 (E, P = 0.000), GSE14323 (F, P = 0.003), and GSE89377 (G, P = 0.000). The original data were plotted using the statistical software R (version 3.5.2). The impact of CA XII expression on OS in HCC patients in the GSE54236 dataset (H, P = 0.002, log-rank test). HCC, hepatocellular carcinoma; GEO: Gene Expression Omnibus; TCGA: The Cancer Genome Atlas; OS, overall survival.