MKI67 and neoplasm: Furthermore, as a reflector of active proliferation, the differentiated prognostic performance of Ki67 in NSCLC may be related to the heterogeneity in proliferative activity and the resulting differences in the biological behaviour of tumours; thus, an integrated analysis of tumour growth, metastatic risk and microenvironment would also help to explain the enigma of prognostic heterogeneity of Ki67 in NSCLC.