IMMUNOHISTOCHEMISTRY OF PNEUMOCYTES IN HYPERPLASIA AND NEOPLASIA

A panel of immunohistochemical markers was employed to evaluate its ut ility in distinguishing between well-differentiated adenocarcinoma of the lung, bronchioloalveolar type, and reactive hyperplasia of type 2 pneumocytes. We studied 20 cases of bronchioloalveolar carcinoma, 10 w ith separate areas of pneumocyte hyperplasia, and 19 cases of non-neop lastic lung conditions with pneumocyte hyperplasia. The panel of marke rs included Leu M-l, B72.3, carcinoembryonic antigen (CEA), both monoc lonal and polyclonal, and human milk-fat globule protein. The sensitiv ities and specificities of these antibodies as ''tumor markers'' are a s follows: Leu M-l, sensitivity 85%, specificity 97%; B72.3, sensitivi ty 80%, specificity 100%; monoclonal CEA, sensitivity 50%, specificity 90%; and polyclonal CEA, sensitivity 50%, specificity 76%. The human milk-fat globule protein was positive in most reactive and neoplastic processes, with a sensitivity of 70% and a specificity of only 3%. The best combination of markers for discriminating between carcinoma and reactive pneumocytes was Leu M-l and B72,3, with 13 of the bronchioloa lveolar carcinomas positive for both, but none of the hyperplasias pos itive for both.