Characterization of basal-like breast cancer: an update

Basal-like breast cancers express genes and proteins associated with the basal layer of mammary epithelium and account for 10-25% of breast cancers. These tumours are of particular interest because they follow an aggressive clinical course and currently lack any form of standard targeted systemic therapy. Over recent years, numerous studies have sought to further characterize this sub-group and dissect out the molecular features that define them. Several biomarkers represent credible novel therapeutic targets and can be evaluated using routine laboratory techniques. As such the basal-like sub-type is becoming increasingly relevant to the histopathologist. However, since recognition of this sub-type is not part of the minimum dataset for breast cancer reporting, many will be unfamiliar with diagnosing these lesions. In this paper, we review the key characteristics of basal-like cancers, discuss closely related entities (triple negative and hereditary breast cancer), and consider the role of molecular markers implicated in these tumours.