Monoclonal antibody 123C3 in lung tumour classification. Immunohistology of 358 resected lung tumours.

Monoclonal antibody 123C3, raised in The Netherlands Cancer Institute against a membrane preparation of small cell lung carcinoma, was tested on a series of 358 surgically resected primary epithelial lung tumours of various types. 123C3 recognized all small cell carcinomas and carcinoids tested (total: 30 tumours), but also stained a minority of various types of non-small cell lung carcinomas and almost all bronchial gland tumours investigated. Staining for 123C3 in squamous carcinomas or adenocarcinomas, when present, was usually focal and weak or moderately strong, whereas staining of small cell carcinomas and carcinoids was strong and present throughout the tumour. Our results indicate that immunostaining for 123C3 may be of potential interest for the histological typing of lung tumours, particularly when staining results are either strongly positive or completely negative. The positivity found in a fraction of non-small cell lung carcinomas is yet another illustration of the fact that the major types of lung tumours cannot be strictly separated, and that overlaps in differentiation states and antigenic make-up exist between different histological types of lung tumours.