TMPRSS2:ERG fusions occur in about 50% of PCa, predominantly in younger patients, and lead to a constituitive overexpression of the transcription factor ERG.42 ERG overexpression by itself lacks prognostic relevance,26 but modulates the expression of more than 1600 genes in prostate epithelial cells. The gene discussed is TMPRSS2; the disease is posterior cortical atrophy.