ER and HER2 expression are positively correlated in HER2 non-overexpressing breast cancer. by Pinhel, I, Hills, M, Drury, S, Salter, J, Sumo, G, A'Hern, R, Bliss, J, Sestak, I, Cuzick, J, Barrett-Lee, P, Harris, A, Dowsett, M