What does the Ki-67 index measure in tumor pathology?

The Ki-67 index is a critical marker used in tumor pathology to evaluate cell proliferation. This index reflects the percentage of tumor cells that are actively dividing within a given population. Ki-67 is a nuclear protein that is only present in cells during the active phases of the cell cycle—specifically during the synthesis (S), G2, and mitosis (M) phases. The presence of Ki-67 is associated with cellular growth, and a higher Ki-67 index often indicates a more aggressive tumor with a rapid growth rate.

In clinical practice, assessing the Ki-67 index can provide valuable prognostic information about the tumor's behavior, guiding treatment strategies and predicting patient outcomes. High levels of Ki-67 may suggest a need for more aggressive treatment, while low levels could indicate a more indolent tumor that might be managed less aggressively.

This differentiation is crucial in oncology, as treatment planning heavily relies on understanding the proliferation status of the tumor. Other options, while related to cellular behavior, do not encompass the specific function and significance of the Ki-67 index in the context of tumor pathology.