OV-TL 12/30 (keratin 7 antibody) is a marker of glandular differentiation in lung cancer

The immunoreactivity of OV-TL 12/30, a monoclonal antibody to keratin 7 was investigated on paraffin-embedded human lung cancer tissues of 61 patients. A modified AEC-immunoperoxidase method with pepsin pre-digestion was used. In normal lung tissue keratin 7 was found in bronchial and bronchiolar epithelium, pneumocytes and compound glands. Squamous metaplasia of the bronchial tree was negative. All 24 squamous cell carcinomas were negative irrespective of grade of differentiation. All differentiation grades of 20 adenocarcinomas including bronchioalveolar carcinomas were positive. Since six large cell anaplastic carcinomas did not react with keratin 7 antibody these tumours are considered to be of squamous cell rather than adenocarcinomatous origin. Small cell anaplastic carcinomas were negative in 10 of 11 cases. Our study demonstrates that this keratin 7 antibody is useful in differentiating between squamous cell carcinoma and adenocarcinoma of the lung and it may be particularly useful in making the correct diagnosis in small lung biopsy specimens.