CDKN2A and hepatocellular carcinoma: Mutations in the TP53, ALK, and ATRX genes, the genes most frequently mutated in both HCC primary tissues and CTCs, were observed in 59%, 24%, and 18% of patients, respectively, and TP53, ARID1A, CDKN2A, CTNNB1, BRIP1, EGFR, FGFR2, RB1, and TSC1 gene mutations with clinical targeted drugs were detected in primary tissues and CTCs from the same patient (Additional file 1: Fig. S7D, n = 17).