Immunohistochemistry with monoclonal antibody B72.3 as an adjunct in the cytologic diagnosis of pancreatic carcinoma.

Due to the morbidity of open tissue biopsy, the cytologic diagnosis of pancreatic carcinoma by fine needle aspiration or examination of biliary tree fluid is highly desirable. Immunohistochemistry with monoclonal antibody B72.3 has been advocated as an adjunct in the identification of tumor cells in body fluids. To assess its usefulness as an adjunct in the diagnosis of pancreatic carcinoma, we examined cytologic specimens of the pancreas from 35 patients [24 pancreatic carcinoma, 6 metastases (4 adenocarcinoma and 1 each of Hodgkin's disease and melanoma), 5 with benign conditions] with an immunohistochemical procedure using B72.3 directly over the Papanicolaou-stained slides. Of the pancreatic carcinomas, 21 of 24 (87%) were cytologically positive and 21 of 24 (87%) marked with B72.3. With both techniques, 23 of 24 cases (96%) could be identified. Three of four metastatic adenocarcinomas were positive by both cytology and B72.3. No staining occurred in the metastatic melanoma, Hodgkin's disease, or 3 of 5 benign conditions. In two benign duodenal aspirates, an unusual reticular B72.3 staining occurred in the mucin of acinar and goblet cells which could be misinterpreted as positive staining. In our experience, B72.3 enhances the sensitivity of the cytologic diagnosis of pancreatic cancer. Unrecognized single tumor cells, cytologically uninterpretable cells, and tumor cell clusters that could be misinterpreted as reactive epithelium mark with B72.3. Care should be taken to avoid misinterpretation of nonspecific mucin staining with this antibody.