KRT19 and lung adenocarcinoma: On the other hand, cytokeratin 19‐fragment (CYFRA21‐1) and carcinoembryonic antigen have been used as tumour markers in human lung adenocarcinoma (Dong et al., 2016; Zhao et al., 2014), and reports indicate that sensitivity increases when these markers are measured simultaneously with serum nectin‐4 (Takano et al., 2009).