The mRNA expression level of all six type IV collagen genes (COL4A1, COL4A2 COL4A3, COL4A4, COL4A5 and COL4A6) was higher in metastatic tissue compared to primary tumor tissue, although being significant only for COL4A3 (p = 0.013) and COLA4A4 (p = 0.005) genes (Supplementary Figure S2). This evidence concerns the gene COL4A2 and neoplasm.