CP and acute lymphoblastic leukemia: Interestingly, although finding foci of ALL cells in the CP, Fernández-Sevilla et al. only exceptionally observed ALL cells transit from the basal to the apical surface of the CP epithelium [139], thus on one hand confirming the presence of ALL in the CP as demonstrated by Williams et al. [129], and on the other hand, confirming the absence of CP BCSFB crossing as described by Yao et al. [130].