Abstract: In 2015, WHO released the fourth edition of the lung, pleura, thymus and cardiac tumor classification. Compared with the 2004 WHO lung tumor classification, the classification of 2015 made a greater change. With the development of the application, pathology doctors and clinicians still have some confusion in some aspects for the understanding and application of the new classification. This paper makes a brief introduction about the new classification of lung tumour, and briefly introduces the main changes of the classification in 2015, and analyzes and discusses the problems that should be paid attention to in clinical practice.

Key words: WHO, lung tumour, classification, pathology