Triple-negative breast carcinomas are defined by a lack of expression of oestrogen (ER), progesterone (PR) and HER-2 receptors. Most of these tumours belong to the basal-like molecular group of breast cancers that express one or more of the basa-myoepithelial cell markers.
We present here an unusual case of an aggressive triple-negative tumour that consisted of two colliding parts, one basal-like and the other appearing to have a more primitive morphology and lacking the expression of basal markers.