POSTN and posterior cortical atrophy: Differently, clinically significant PCa—classified as PGG2 (GS = 3 + 4) and PGG ≥ 3 (GS ≥ 4 + 3)—showed a high percentage of medium/strong peritumoral periostin staining, which increased progressively with the increase intumor grade, resulting associated with the aggressiveness of the disease (Chi-Square p-value < 0.0001).