PLA2G4A and cholangiocarcinoma: Studies have shown that the PLA2G4A gene can be used as a biomarker in various diseases such as gastric cancer (Bazhan and Khaniani, 2018), acute myeloid leukemia (Hassan et al., 2021; Lai et al., 2021), cholangiocarcinoma (Sun et al., 2019), and colorectal cancer (Zhan et al., 2021a).