Staining was completelyabsent in normal pancreas and pancreatitis, but frequent in pancreatic cancer.Membranous and cytoplasmic MUC5AC expression was most common in pancreaticadenocarcinomas (71% of 423), followed by carcinomas of the ampulla Vateri (43%of 47), and absent in six acinar cell carcinomas. The gene discussed is MUC5AC; the disease is familial pancreatic carcinoma.