Exclusively associated to the fourth cluster (green, highest malignancy) are genes applicable to discriminating the highly agressive tumors from the mucinous, such as the fibroblast growth factor 2 (FGF2, consistent with [27]), the Clostridium perfringens enterotoxin receptor (CPE-R) which was discussed in context of prostate cancer [28], and Glutathione [29]. Here, CLDN4 is linked to prostate cancer.