My research in thoracic neoplasms has focused on lung cancer, malignant mesothelioma, and mediastinal thymic tumors. I have worked on classification of thoracic disorders and served as Lead Editor of the 1999 WHO Classification of Lung and Pleural Tumors as well as the 2004 and 2015 WHO Classification: Pathology and Genetics of Tumors of the Lung, Pleura, Thymus and Heart. I also led the 2011 IASLC/ATS/ERS lung adenocarcinoma classification.

My interest in non-neoplastic lung disease has focused on interstitial lung disease. This resulted in my leading the 2002 American Thoracic Society and European Respiratory Society International Multidisciplinary Consensus Classification of Idiopathic Interstitial Pneumonias; the 2008 ATS Project on Nonspecific Interstitial Pneumonia; and the 2012 ATS/ERS: Update of the International Multidisciplinary Classification of the Idiopathic Interstitial Pneumonias.