Basal-like Breast Carcinomas: Identification by P-cadherin, P63and EGFR Basal Cytokeratins Expression

ABSTRACT

Invasive breast carcinomas constitute a heterogeneous group of tumours, with different clinical behaviour and response to chemotherapy. These lesions, as determined morphologically, are thought to arise exclusively from the inner, luminal epithelial cell compartment of the terminal-duct lobular unit of the breast. Irrespective of the true histogenesis of breast carcinomas, ithas become increasingly clear that a small proportion of cancers exhibit a basal/myoepithelial phenotype as defined by immunohistochemical positivity for myoepithelial markers, meaning they express molecules normally seen in the basal/myoepithelial compartment of the normal breast. The purpose of this review is to resume the more recent knowledge about the use of a panel of basal molecular markers in “basal-like” breast carcinomas classification and characterization. This subtypecharacterization has a great importance, since it requires a more focused investigation of putative therapeutic targets. The existing therapies against estrogen receptor (ER) or HER-2 oncogene amplification would not be expected to be effective against basal breast carcinomas, since these tumours express neither of these proteins. In contrast, basal breast carcinomasusually express basal cell cytokeratins (like CK5/6), P-cadherin adhesion molecule, p53 family member p63, and the transmembrane tyrosine kinase receptor EGFR (epidermal growth factor receptor), which can be used as excellent markers for this line of mammary carcinogenesis, and become interesting therapeutic targets against these highly aggressive lesions.