EGFR analysis: current evidence and future directions.

Until a few years ago, only lung cancer histological specimens were considered suitable for testing epidermal growth factor receptor (EGFR) mutations. Then, several retrospective studies were designed to test EGFR mutation on a sizeable number of parallel cytological and histological samples obtained from the same patients and, even more recently, several institutions reported their prospective clinical experiences on routine specimens. Basing on these studies the College of American Pathologists, the International Association for the Study of Lung Cancer, and the Association for Molecular Pathology have recently considered cytological samples suitable for EGFR testing. Therefore, it seems timely to draw together the threads of this large body of information in order that cytopathologists can be knowledgeable partners in the multidisciplinary process of targeted cancer therapy and to help refine current testing guidelines. This review addresses (1) the more common proposed techniques including the use of direct cytologic smears cell blocks and liquid based cytology; (2) the issues related to current practice, which in Europe is external centralized testing that is usually done on samples containing very few cells; and (3) the future directions based on the implementation on lung cytology of next generation sequencing approaches.