Lung cancer is an extremely heterogeneous disease, with well over 50 different histological variants recognized under the fourth revision of the World Health Organization (WHO) typing system. Because these variants have differing genetic and biological properties correct classification of lung cancer is necessary to assure that lung cancer patients receive optimum management. Due to the recent understanding that histologic typing and EGFR mutation status are important for target the therapy in lung adenocarcinoma patients there was a great need for a new classification that addresses diagnostic issues and strategic management to allow for molecular testing in small biopsy and cytology specimens. For this reason and in order to address advances in lung cancer treatment an international multidisciplinary classification was proposed by the International Association for the Study of Lung Cancer (IASLC), American Thoracic Society (ATS), and European Respiratory Society (ERS), further increasing the histological heterogeneity and improving the existing WHO-classification. Is now the beginning of personalized therapy era that is ideally finalized to treat each individual case of lung cancer in different way.