In order to select optimal candidate RGs for this study on ovarian tumours, ΔCt between one benign and one malignant ovarian tumour sample with the greatest difference in expression of the traditionally used RGs (ACTB, GADPH, and HPRT1), was measured by RT-qPCR and calculated for all 32 genes included in the arrays. Here, HPRT1 is linked to cancer.