Abstract: The International Agency for Research on Cancer (IARC) published the WHO classification of thoracic tumours (5th edition) in May 2021. Compared with the 4th edition published in 2015, the 5th edition changed the framework of the main chapters and added/adjusted the nomenclature and classification of some tumours. The 5th edition enriched the epidemiology, etiology, histopathology, molecular genetics and other related content.This article briefly introduced the major changes in the classification of the pleura, pericardium and thymus tumours in the WHO classification of thoracic tumours (5th edition).

Key words: 2021 WHO classification, Pleura tumours, Pericardium tumours, Thymus tumours