UPK2 and colorectal carcinoma: Considering the primary role of UPK2 as the permeability barrier of the urothelium, we hypothesize that UPK2 could potentially facilitate the formation of micropapillary structures, and MUC16, that we also identified as a marker for micropapillary CRC, could further contribute to the protective epithelial barrier function of micropapillary structures by providing a hydrophilic environment.