Relative quantity of each candidate EC. (A) Quantity of the candidate endogenous control genes let-7a, miR-10b, miR-21, miR-16, miR-26b, RNU48 and Z30, relative to calibrator (normal tissues) and corrected for amplification efficiency (Q. rel = E-ΔCt), in the benign (BEN, clear ), bone metastases (BM, dark), metastases free (MF, dashed) and visceral and bone metastases (VBM, shaded) groups. The boxes show the interquartile range and median, whiskers indicate the range and outliers are depicted with the symbol (*). No difference was found within gene between the tissue subgroups (P>0.05) thus establishing the validity of EC comparison. (B) Variation associated with candidate endogenous control genes. Relative quantity of each gene is relative to calibrator (normal tissues) and corrected for amplification efficiency (Q.rel = E-ΔCt). There was no significant difference in variance associated with relative gene expression (P > 0.05).