This resulted in our identification of a PCa-associated aberrant glycosylation of PSA, which produces α2,3-linked sialyl N-glycan that is readily observed on free PSA (S2,3PSA), whereas α2,6-linked sialyl N-glycan on free PSA (S2,6PSA) is exclusive to benign prostatic hyperplasia (BPH) [18] (Figure 1). This evidence concerns the gene KLK3 and benign prostatic hyperplasia.