CD44 and primitive neuroectodermal tumor: As shown in Table 4, CD44 expression was significantly associated with PD-L1 expression (p = 0.030, OR: 9.429, 95% CI: 1.058–84.037) and marginally associated with PNET tumor type (p = 0.053, OR: 4.242, 95% CI: 0.935–19.256).