Re: Korschinget al. The origin of vimentin expression in invasive breast cancer: epithelial-mesenchymal transition, myoepithelial histogenesis or histogenesis from progenitor cells with bilinear differentiation potential?J Pathol 2005; 206: 451-457

Morphologic and molecular evolutionary pathways of low nuclear grade invasive breast cancers and their putative precursor lesions: further evidence to support the concept of low nuclear grade breast neoplasia family

We have previously provided evidence showing an association between some precursor lesions with low nuclear grade breast carcinomas (LNGBCs). In this study, further immunophenotypic support to our proposed route of pathogenesis of LNGBC and their precursor lesions was provided. Precursor lesions including columnar cell lesions, atypical ductal hyperplasia, ductal carcinoma in situ, usual epithelial hyperplasia, and lobular neoplasia were compared with matching "morphologically normal" terminal lobular duct units and matching invasive carcinoma. The epithelial cells in the putative precursor flat epithelial atypia, atypical ductal hyperplasia, lobular neoplasia, ductal carcinoma in situ lesions, and their coexisting LNGBC were negative for basal and myoepithelial markers, but positive for CK19/18/8, estrogen receptor (ER)-alpha, Bcl-2, and cyclin D1. The ER-alpha/ER-beta expression ratio increased during carcinogenesis, as did expression of cyclin D1 and Bcl-2. p53 immunopositivity was found 3% in LNGBC versus 43% in high nuclear grade breast carcinoma (HNGBC), whereas ataxia telangiectasia mutated expression was absent or reduced in 22% of LNGBC versus 53% of HNGBC cases. In summary, our findings support the concept that flat epithelial atypia is the earliest morphologically identifiable nonobligate precursor lesion of LNGBC. These may represent a family of precursor, in situ and invasive neoplastic lesions belonging to the luminal "A" subclass of breast cancer. The balance between ER-alpha and ER-beta expression may be important in driving cyclin D-1 and Bcl-2 expression. Ataxia telangiectasia mutated may be one of the alternative regulatory mechanisms to TP53 mutation or dysfunction in low-grade and high-grade breast carcinoma. Our findings support the concept that progression of LNGBC to HNGBC (basal-like or HER2+) phenotype is an unlikely biologic phenomenon.

Triple negative breast carcinoma and the basal phenotype: from expression profiling to clinical practice

Triple negative breast carcinomas (TNBCs) are a group of primary breast tumors with aggressive clinical behavior. Most TNBCs possess a basal phenotype (BP) and show varying degrees of basal cytokeratin and myoepithelial marker expression. The importance of recognizing these tumors came to light largely as the result of gene expression profiling studies that categorized breast cancer into 3 major groups. Two of these groups are defined by their respective expression of estrogen receptor and HER2. TNBCs represent a third group and are defined by negativity for hormone receptors and HER2. TNBCs currently lack effective targeted therapies and are frequently resistant to standard chemotherapeutic regimens. These tumors tend to occur in premenopausal women and members of specific ethnic groups and a subset are associated with heritable BRCA1 mutations. For patients with sporadic TNBCs and BP tumors, BRCA1 dysfunction seems to play a major role in the development and progression of disease. The pathologist's role in the diagnosis and characterization of TNBCs and BP tumors is currently being defined as we are acquiring knowledge of the biologic and genetic underpinnings that drive this heterogeneous group of diseases. This review will provide a historical prospective on TNBCs and tumors that express basal cytokeratins and myoepithelial makers. Additionally, we will discuss the molecular biologic, genetic and pathologic aspects of these tumors. Guidelines will be provided on how to best approach the diagnosis of these cases and on what input pathologists should provide clinicians to help develop optimal therapeutic and preventative strategies against this aggressive group of breast cancers.