This category contains cancer types arising from CK18 positive precursor cells but showing CK18 downregulation in a fraction of cases, tumor types arising from CK18 negative precursor cells but undergoing CK18 upregulation in a fraction of cancers, neoplasia’s derived from tissues with variable CK18 expression in benign precursors, and tumors with a mixed differentiation. The gene discussed is KRT18; the disease is neoplasm.