MUC5AC and tubular adenocarcinoma: In addition, high levels of CEACAM6 are suggested as a screening parameter especially for eCCA (Rose et al. 2016), which is consistent with our data showing overexpression of CEACAM6 in LD-iCCA, as LD-iCCA are generally mucin-secreting tubular adenocarcinomas resembling perihilar and distal CCA (Kendall et al. 2019).