Second, a substantial proportion of TNBC samples (~13–16 %) coming from the Lehmann et al. [17] classification were either not considered to be TNBC by gene expression and are removed (i.e. ESR1-high), or they fall into the unclassified or unstable (UNS) group, which is composed of a mix of tumors that only share the feature that they cannot be classified into one of the other six tumor subtypes. Here, ESR1 is linked to neoplasm.