The relative degree of heterogeneity of various breast cancer subtypes. The intrinsic subtypes have been ranked from the left (yellow) to the right (red) according to their heterogeneity degrees in which Luminal A and Basal-like are poorly and highly heterogeneous, respectively. The second row shows the overlap of the intrinsic based subtype classification with that of IHC based. The last row shows the availability of targeted therapy for each subtype. The relatively more heterogeneous Basal-like and Claudin-low are the subtypes with very poor prognosis since no therapeutic has been tailored to their biology thus far (See the text).