Recent advances in the pathology and molecular genetics of lung cancer: A practical review for cytopathologists

Lung cancer is one of the most common causes of cancer-related death worldwide. Better understanding of the molecular genetic characteristics of non-small cell lung carcinoma (NSCLC), particularly adenocarcinoma, has opened the opportunity for targeted therapies. With the different molecular abnormalities and the different responses to new targeted therapies based on the histological subtype of NSCLC, there came a need to further classify NSCLC into squamous cell carcinoma and adenocarcinoma, and to perform the appropriate molecular testing in these different subtypes to guide management decisions. Given that approximately 70% of lung cancer patients have only small biopsies or cytology specimens available, incorporating the testing of these specimens into the cytopathology laboratory has been crucial. Herein, we review current concepts and recommendations on NSCLC subtyping and molecular testing that are relevant for the cytopathology community.