Update on histologic classification of non-small cell lung cancer

Given the recent advances in personalized medicine in lung cancer that are mostly observed in adenocarcinomas, an international multidisciplinary group of lung cancer specialists has recommended a new sub-classification of resected adenocarcinomas, and a histologic classification in small biopsies and cytologic material that constitutes the majority of specimens. Whereas the classification of adenocarcinomas has been shown to have better correlation with prognosis than the current WHO classification, it has brought many questions that need to be addressed. In order to further classify poorly-differentiated NSCLC while preserving tissue for molecular testing in small samples, a minimal 2-marker panel of immunohistochemistry (TTF-1 and 63/p40) has been recommended. In the current WHO classification, squamous cell carcinoma and large cell carcinoma categories include several variants, some of which are based solely on cytomorphologic features and do not appear to have biologic significance. Thus, a new, biology-based sub-classification is also warranted in those categories.