Immunocytochemical study of RAS oncoprotein in cytologic specimens of primary lung tumours.

We have examined the distribution of ras p21 oncoprotein expression in cytologic specimens from 73 primary bronchial carcinomas using an immunocytochemical analysis. The cytologic preparations studied represent the two major groups of histological types of lung cancer: Small Cell Lung Carcinoma (SCLC) and Non-Small Cell Lung Carcinoma (NSCLC) (squamous cell carcinoma and adenocarcinoma). The differential expression of ras p21 oncoprotein correlated with histological classification and was found in 30% of 23 small cell lesions, 61% of 28 squamous cell lung carcinomas and 32% of 22 adenocarcinomas. The ras p21 oncoprotein was commonly expressed in NSCLC cases (48%) as compared to SCLC cases (30%).