Triple-negative breast cancers (TNBCs) are defined as tumours that are negative for oestrogen, progesterone and HER-2 receptors. At a percentage of 10-20% TNBCs represent a minority in all breast cancers. However, because of the poor prognosis of this particular subtype, triple negative disease accounts for a disproportionate number of metastatic cases and breast cancer deaths. Identification of its subtypes is essential for understanding the biological characteristics and clinical behaviour of TNBC, as well as for developing personalised treatments.