New WHO classification of breast tumours – as published in 2019

Abstract

At the end of 2019, a new classification of breast malignancies was published by the World Health Organization (WHO). Popular name of the classification is the "blue book" and it derives from the colour of its cover. New classification was made available after 7 years from the previous one. In 2019 the WHO introduced new disease entities: mucinous cystad­enocarcinoma and tall cell carcinoma of reverse polarity. The most recent classification also contains classification of the microscopic evaluation of ductal carcinoma in situ (DCIS) and of the evaluation of the parameters necessary to define the tumour grade of breast cancer as well as predictive or prognostic parameters. All of above mentioned changes are presented and commented on in the article.