NCAM1 and periventricular leukomalacia: In PVL (Figure 4A) and OL (Figure 4C) cases, CD56 immunostaining was predominantly observed in cells in the subepithelial connective tissue, with scarce positive intraepithelial cells, with 7/8 cases and 7/10 cases presenting a final score ≥ 4 in PVL and OL group, respectively (Figure 2C, Table S2).