Improvement of the clinical applicability of the Genomic Grade Index through a qRT-PCR test performed on frozen and formalin-fixed paraffin-embedded tissues. by Toussaint, J, Sieuwerts, A, Haibe-Kains, B, Desmedt, C, Rouas, G, Harris, A, Larsimont, D, Piccart, M, Foekens, J, Durbecq, V, Sotiriou, C