Correlation of results obtained from RQ-PCR analysis of paired fresh-frozen and FFPE tissues. Scatter plot matrix (left panel, A) showing normalized gene expression data obtained by RQ-PCR analysis of the 19 fresh-frozen vs. FFPE sample pairs (n = 38 samples). The pair-wise Pearson product-moment correlation coefficient was 0.50 (p < 0.0001). The right panel (B) shows a heatmap analysis for the Pearson correlation of gene expression abundance as determined by RQ-PCR, for all pair-wise combinations of samples. A low-moderate correlation is observed between mRNA transcript quantification data in fresh-frozen vs. FFPE tissues, and tissues tend to cluster according to storage method.