Immunohistochemical labeling for the Dpc4 gene product is a specific marker for adenocarcinoma in biopsy specimens of the pancreas and bile duct

We immunohistochemically labeled 72 biopsy specimens from the extrahepatic biliary tree and pancreas for Dpc4 protein and correlated expression with h istologic diagnosis and patient follow-up. Specimens were classified histol ogically as follows: nonneoplastic, 35; neoplastic, 22; atypical, 15. Loss of expression of Dpc4 protein was identified in 12 specimens; 11 were histo logically diagnostic of carcinoma. The 12th specimen was from a patient who se biopsy specimen initially was diagnosed as "atypical," but clinical foll ow-up revealed adenocarcinoma. Of the 12 atypical biopsy specimens with int act expression for Dpc4, follow-lip later revealed that 10 were adenocarcin oma. Loss of expression of Dpc4 protein was never identified in a benign sp ecimen. Immunohistochemical labeling for the Dpc4 gene product is a specific marker of carcinoma in biopsy specimens of the pancreas and extrahepatic bile duc ts and is marginally helpful in classifying atypical specimens. The sensiti vity for carcinoma is low. This latter finding is not unexpected, because t he DPC4 tumor suppressor gene is inactivated in only about half of pancreat ic and biliary malignant neoplasms. Importantly, loss of Dpc4 expression ha s been reported in in situ carcinomas, suggesting that loss of expression s hould not be equated with invasive carcinoma.