The 2019 World Health Organization classification of tumours of the breast

The classification of breast tumours continues to evolve, with the integration of new knowledge from research rapidly being translated into clinical practice. Major changes are shown in Table 1. In this volume of the World Health Organization (WHO) classification of tumours series’ fifth edition, which is an update of the fourth-edition breast tumours volume published in 2012,1 the descriptions of breast tumours follow the familiar systematic approach of previous volumes, with the content now organised in sequence from benign epithelial proliferations and precursors, through benign neoplasms, to in-situ and invasive breast cancer, followed by mesenchymal and haematolymphoid neoplasms, tumours of the male…