Utility of surfactant protein B precursor and thyroid transcription factor1 in differentiating adenocarcinoma of the lung from malignant mesothelioma

Differentiation of malignant mesothelioma from adenocarcinoma, particularly from a lung primary, remains a difficult diagnostic problem. Surfactant pr otein B precursor (pro-SP-B) and thyroid transcription factor 1 (TTF-1) are expressed selectively in the normal respiratory epithelium and in adenocar cinomas of the lung. In this study, we evaluated the utility of pro-SP-B an d TTF-1 in distinguishing pulmonary adenocarcinomas and malignant mesotheli omas. Immunoreactivity for pro-SP-B and TTF-1 was examined in paraffin sect ions of 370 primary hmg carcinomas (208 adenocarcinomas, 101 squamous cell carcinomas, and 61 large cell carcinomas) and 95 malignant mesotheliomas, u sing a pro-SP-B antiserum and a monoclonal TTF-1 antibody with a biotin-str eptavidin detection system. Immunostaining for pro-SP-B was detected in 57% of adenocarcinomas, and 20% of large cell carcinomas. Immunoreactivity for TTF-1 was shown in 76% of adenocarcinomas and 26% of large cell carcinomas . Malignant mesotheliomas and squamous cell carcinomas did not stain with e ither antibody. The expression of pro-SP-B and TTF-1 in adenocarcinomas of the lung but not in malignant mesotheliomas shows that pro-SP-B and TTF-I s taining is useful in differentiating these neoplasms. Copyright (C) 1999 by W.B. Saunders Company.