Is 'basal-like' carcinoma of the breast a distinct clinicopathological entity? A critical review with cautionary notes.

This review deals with studies that have used cDNA microarrays and immunohistochemistry to identify a subtype of breast carcinoma known as basal-like carcinoma. The key breast carcinoma studies are critically discussed to highlight methodological problems in cohort selection, definitions, interpretation of results and statistical analysis. The review concludes that basal-like carcinomas do not reflect a single, biologically uniform group of breast cancers, but show significant variations in their phenotypes, grades, immunoprofiles and clinical behavior, just as a wide range of subtypes and behaviors is observed among epithelial/luminal-derived breast carcinomas. Well-designed studies with comparison of low-grade nonbasal versus low-grade basal and high-grade nonbasal versus high-grade basal carcinomas are necessary before one can be convinced that this subtype represents a distinct clinicopathological entity.