MKI67 and neoplasm: Ki-67 is useful in determining the proliferation index of cells, which is the percentage of cells in a tissue sample that are positive for Ki-67.5A high Ki-67 index indicates a high level of cell proliferation and is often associated with aggressive tumor behavior.6In various cancers, including ameloblastoma, a higher Ki-67 labeling index is generally associated with more aggressive disease, increased likelihood of metastasis, and poorer prognosis.