Remarkable advances have occurred since the Series 3 Fascicle published in 1995 with paradigm shifts in every dimension of our understanding of lung tumors including clinical, radiologic, histopathologic, cytopathologic, immunohistochemical, molecular and therapeutic aspects. The molecular revolution leading to effective targeted therapies and breakthroughs in immunotherapy for lung cancer have led to novel approaches incorporating the concept of personalized medicine for patients who historically had little hope. These advances have strengthened the place of pathologists to play a central role in the multidisciplinary team that is now needed to properly diagnose and manage lung cancer patients.

The new WHO Classification of Lung and Pleural Tumours updates the previous proposal from 1981 and incorporates many new concepts that have developed since that time. A number of newly described lesions are included as well as current concepts in papillomas, adenomas, neuroendocrine tumours, adenocarcinomas, mesothelial tumours, and carcinomas with pleomorphic, sarcomatoid and sarcomatous features. The result is a comprehensive classification with detailed definitions and explantory notes illustrated by 150 high quality color photomicrographs that will promote uniformity in recording and reporting data nationally and internationally. The WHO panel consisted of 24 members from 14 countries giving a broad international input into this work.