CD44 and Balkan nephropathy: PLUM regression analysis of expression CK5/6, CD44, and CK20 in control UTUC showed that differentiation had a predictive influence on expression of the basal compartment and superficial markers (Wald = 4.404, p = 0.036) and on necrosis in BEN tumors (Wald = 7.707, p = 0.006) (Table 4).