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Hellenic Archives of Pathology, Volume 22, Issues 1-3, 2008, 7-14
Basal like breast carcinomas
Theohari E., Nakopoulou L.
First Department ïf Pathology, University Medical School ïf Athens
Recent advance in molecular medicine and genetics has led to a new classification of breast cancer, the most frequent malignancy of women. This taxonomy is based on gene expression patterns and there are 5 subtypes: luminal type A, luminal type B, normal breast-like, HER2 and basal-like breast carcinomas. Basal-like breast carcinomas comprise a new molecular subtype characterized by the expression of proteins that are characteristic of the basal/myoepithelial breast cells. Their main feature is the lack of hormonal receptors (ER, PR) and HER2 expression, the so-called "triple negative" phenotype, in association with the expression of high molecular weight cytokeratines (such as CK5/6, CK14 and CK17) and EGFR. However, it should be noted, that basal like carcinomas have usually, but not always, "triple-negative" phenotype. From the above, it is obvious that no generally accepted determination exists so far for basal like carcinomas, and they are characterized as such from the study of many markers. Even if they belong to the class of sporadic carcinomas, they share common features with hereditary cancer related to BRCA1 mutations. Although no somatic mutations have been found in the basal like carcinomas, it seems that some epigenetic changes (e.g. promoter methylation of BRCA1) induce the aberrant function of the BRCA1 regulated-pathway, giving rise to carcinomas with a basal phenotype. The predominant hypothetical model of their origin is that of stem cells. According to this theory, the accumulation of mutations interrupts their further differentiation in an early stage, during of which basal/myoepithelial cells have been produced, giving rise to basal-like carcinomas. All 5 molecular subtypes of breast carcinoma have been related to different prognosis. The immunophenotypic characteristics of breast carcinomas with a basal phenotype are associated with aggressive biological behavior and, indeed, it has been shown that these tumors are of poor prognosis characterized by poor patients' overall survival. For this reason, further inspection is needed so that efficient treatment approaches will be discovered in the future.
Key words: Cancer, breast, basal-like.
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