[Classification of preinvasive breast and carcinoma in situ: doubts, controversies, and proposal for new...

As a consequence of increased screening mammography, preinvasive breast lesions represent a growing percentage of breast pathology diagnoses. Intraductal epithelial proliferations of the breast are, at present, classified into three groups: usual epithelial hyperplasia, atypical ductal hyperplasia and ductal carcinoma in situ. The boundary between those two last entities is not clearly defined on a morphological point of view although the clinical management is different. Columnar atypical lesions or flat atypical hyperplasia, frequently observed near microcalcifications, are not homogeneously managed. Lobular lesions are classified under the category of lobular neoplasia which avoid interobserver variability. Molecular biology data and immunoprofiles isolate different lobular phenotypes and link them to invasive cancer. The different systems of classifications of those different entities, the most recent molecular biology datas, controversies and consensus are described in this manuscript.