WHO classification of the tumor of the breast, 2012 (1) The new WHO classification of tumor of the breast has been published in 2012. It is fourth edition. It provides a timely update to many aspects of breast cancer classification, because our understanding of the pathology, genetics and molecular biology has progressed since 2003. New classification covers not only invasive breast carcinomas, but also precursor lesions, lesions of low malignant potential, benign epithelial proliferations, and non-epithelial neoplasms. Invasive carcinoma of no special type. First thing that has been changed is terminology of invasive breast carcinoma. Previously used term “invasive ductal carcinoma, not otherwise specified” has been replaced by “invasive breast carcinoma of no special type”. It is logical, because using of the term “ductal” was not always correct. Derivation of all these tumors from the ductal system is not always proven. Thus, now there are carcinomas of NST and special types of breast carcinomas, for example, lobular, tubular, cribriform, metaplastic, apocrine, mucinous, papillary and micropapillary carcinoma, as well as carcinoma with medullary, neuroendocrine and salivary gland/skin adnexal type features. Mixed tumors, which contain elements of NST and special type carcinomas, are designated now as mixed invasive NST and special type or mixed invasive NST and lobular carcinoma.