SummaryThe developments in gene expression analysis have made it possible to sub-classify hormone receptor-positive (luminal) breast cancer in different prognostic subgroups. This sub-classification is currently used in clinical routine as prognostic signature (e.g. 21-gene Onoctype DX®, 70-gene Mammaprint®). As yet, the optimal method for sub-classification has not been defined. Moreover, there is no evidence from prospective trials. This review explores widely used genomic signatures in luminal breast cancer, making a critical appraisal of evidence from retrospective/prospective trials. It is based on systematic literature search performed using Medline (accessed September 2013) and abstracts presented at the Annual Meeting of American Society of Clinical Oncology and San Antonio Breast Cancer Symposium.