CD33 and cholangiocarcinoma: Based on the observation that MDSCs and monocytes are differentially increased in the circulation of patients with hepatobiliary malignancies, we analyzed the innate immune cell infiltration pattern via immunohistochemistry staining of CD45, the pan-myeloid marker CD33 and MHC Class II (HLA-DR) in a subset of patients with HCC, CCA, NET, CRLM and benign lesions (Fig. 2A).