Delving deeper into understanding of the role of the endocrine system in the development of TNBC tumours created the possibility to re-evaluate SERMs for treatment of this subtype of breast cancer.8,9 For instance, it was shown that a specific isoform of ERα (e.g. ERα36) mediates the oestrogen signalling pathway participating in specific transcriptomic signatures of TNBC.10,11 4-Hydroxytamoxifen (II, Fig. 1) is an active metabolite of tamoxifen (I, Fig. 1)12,13 (SERM of the first generation) serving as an antagonist of ERα in breast tissue. This evidence concerns the gene ESR1 and neoplasm.