The tumor cell cytoplasm is marked in 90% of cases by CTK7, CTK19, epithelial membrane antigen (EMA; Muc-1), epithelial adhesion molecule (EpCAM), and CEA (Table 3), which are indicators of bile duct differentiation, along with nuclear staining for transcription factors Sox-9 and Sox-10 (Lee et al. 2006; Brunt et al. 2015; Yin et al. 2012; Goodman et al. 1985; Vinay et al. 2023). The gene discussed is MUC1; the disease is neoplasm.