This approach has clear limits: (a) only gene expression data are used, (b) not all the data have been raised in controlled studies aimed at the identification of prostate cancer biomarkers, and (c) not all markers are represented in the dataset used (in particular, the non-coding RNA marker PCA3/DD3 [14] that is widely used in combination with PSA was not present in the dataset analyzed). The gene discussed is KLK3; the disease is prostate carcinoma.