REG4 and mucinous adenocarcinoma: REG4 expression was less frequently observed in colorectal cancer than in adjacent non-neoplastic mucosa, in well- and moderately-differentiated adenomas than in mucinous carcinoma (Zheng et al., 2011), and in the cancers of the right colon than in the left colon and rectum, respectively (Kang et al., 2021).