1999 and 2004 WHO classifications of lung cancer has used widely with few major advances for about 10 years. Recently the lung cancer classification has changed to a markedly evolving field with rapid progression of molecular discovery in the lung adenocarcinoma. The exact pathologic diagnosis and subclassification of the non-small cell lung carcinoma in small biopsies and cytologic specimens are key roles in the clinical management of lung cancer patients. We need special stains or immunohistochemical stains using several useful markers as an aid to diagnosis, particularly in the setting of poorly differentiated tumors that do not show clear differentiation by light microscopy. Also every institution needs to develop a multidisciplinary cooperation system to make an exact diagnosis and plan an appropriate targeted treatment in the patients with lung cancer. In this article, we describe the concept and diagnostic criteria of the 2011 IASLC/ATS/ERS classification of nonsmall cell lung carcinoma in the small biopsy and resected specimens.