Classifications and prognosis of breast cancer: from morphology to molecular taxonomy

In 2003, the WHO breast tumours classification was published. It was primarily histological, but in each chapter, a section of cytogenetic as well as molecular pathology was present. The various problems of terminology were solved introducing for each histological group a paragraph where most of the synonyms were included. When an agreement was not reached, a table was presented where the different terminologies were compared. This was mostly evident for the intraductal neoplastic proliferations and accordingly the traditional terminology of Ductal Carcinoma in Situ was taken in consideration, together with the "novel" terminology of Ductal Intraepithelial Neoplasia. Using microarrays, Sorlie et al. were able to classify breast cancer along six different categories of which basal-like was at an extreme representing the most undifferentiated tumours and luminal subtype A represented the majority of their cases which probably were the most differentiated. The advantages and disadvantages of the recent molecular classifications are discussed.