Critical Role of Pathologists in the Accurate Subclassification of Non-Small Cell Lung Carcinoma (NSCLC) for Targeted Therapies: Evidence- Based Practice and the Role of IHC Markers.

Lung cancer is one of leading causes of cancer-related deaths worldwide. Recent genetic study has identified several driver gene mutations, which leads to the development of targeted therapies and our knowledge in lung cancer. In 2015, the WHO classification of lung cancer and the IASLC (International Association of Study of Lung Cancer) have updated their criteria and recommendation in lung cancer [1]. They emphasize the importance of accurate subclassification of lung cancers for targeted therapy. Clinically, the majority of lung cancer patients present with locally advanced disease or with distant metastasis at the time of diagnosis, and surgical resection of the tumor for morphological evaluation may not be the option. Thus, fine needle biopsy of the tumor become an important approach for diagnosis and staging of lung cancer as well as for molecular characterization of the tumor [2]. However, lung cancer is a heterogeneous group of neoplasms and accurate diagnosis on small biopsies can be challenging [1,2].