Ki-67 in meningioma: distribution and implications

In a groundbreaking study published in the Journal of Neurosurgery, we unraveled the true biological meaning of Ki-67, one of the most widely used markers of tumor proliferation in meningioma. Using single-cell mass cytometry and RNA sequencing across more than 120,000 cells, our team discovered that Ki-67 is not expressed solely by tumor cells, as long assumed, but also by immune populations, particularly myeloid cells in low-grade tumors. We further showed that the cellular sources of Ki-67 shift with tumor grade, radiation exposure, and patient age, revealing how immune activity can confound traditional proliferation indices. By integrating molecular data from nearly 500 additional meningiomas, we established dynamic Ki-67 thresholds that more accurately predict recurrence over time. Together, these findings redefine how proliferation is measured in meningioma and lay the groundwork for a new, microenvironment-aware framework for interpreting tumor biology and guiding clinical decisions.