Ki-67

Ki-67 is a protein found in cells that are actively dividing, and pathologists measure it to gauge how fast a tumor is growing. The result, called the Ki-67 index, is the percentage of tumor cells that test positive for it. A higher index generally means a more aggressive, faster-growing cancer.

Origin

Ki-67 was discovered in the early 1980s by researchers in Kiel, Germany; the "Ki" stands for Kiel and "67" was the number of the original antibody clone. It has since become a standard marker of cell proliferation in cancer pathology.

Significance in Asbestos Context

In mesothelioma and asbestos-related lung cancer, a Ki-67 index helps doctors judge how aggressive the tumor is and can inform prognosis and treatment decisions. A high proliferation index may support a more aggressive treatment approach and can factor into estimates of survival. Because it appears in the pathology report, the Ki-67 value can also be part of the medical record used to describe disease severity in a claim. Patients can ask whether Ki-67 was measured and what their index means for their outlook.

Example Sentence

Her pathology report listed a Ki-67 index of 40 percent, which the oncologist said pointed to a more aggressive epithelioid mesothelioma.

Related Terms

Immunohistochemistry, Histological Grading, Proliferation Index, Prognosis, Epithelioid Mesothelioma, BAP1

Notes

• Ask your oncologist whether Ki-67 was tested and how your index compares with typical ranges for your tumor type.
• Ki-67 is one factor among several (cell type, stage, BAP1 status); don't read it in isolation.
• Keep the full pathology report; the Ki-67 index and other markers may matter for both treatment and documenting severity.