MKI67 and neoplasm: Four patients whose tumor showed large central necrosis (CN) with a ring-like enhanced wall with a relatively smooth margin and was accompanied by only focal edema on MRI (Group IIIa) were considered the low invasion (Lo-I) type, and they all presented with high proliferative activity (Ki-67 SI (42.1 ± 7.2%)) in the tumor periphery.