MKI67 and central nervous system cancer: However, Ki-67 sometimes has a detrimental influence on the grading process, as shown in Case 2, because Ki-67 PI of grade III gliomas largely overlaps with that of grade IV (Shibata et al., 1988; Kayaselçuk et al., 2002; Johannessen and Torp, 2006; Skjulsvik et al., 2014).