CD63 and posterior cortical atrophy: However, when the low- and high-grade PCa patients were independently analyzed, the CD63 expression was significantly higher in patients with PCa Grades III–V (shown in Figure 1) compared to those with PCa Grades I–II (respectively, 6.24 (0–9) vs. 1.57 (0–6) score), and there was an association between CD63 expression score and PCa grade groups (Pearson’s χ2 = 0.59; p < 0.0001), as shown in Figure 1 and Figure 2.