MUC1 and biliary tract neoplasm: The 73 included case reports and case series encompassed a broad spectrum of epithelial malignancies, which were classified into 14 major organ-based categories. Among the included TA-MUC1-positive cases, pancreatic cancer was most frequently reported (n = 14, 19.2%), followed by colorectal cancer (n = 10, 13.7%), biliary tract cancer (n = 9, 12.3%), and gastric cancer (n = 6, 8.2%).