Ki-67 IHC Marker

Function

The Ki-67 protein is a cellular marker strictly associated with cell proliferation. It is present during all active phases of the cell cycle (G1, S, G2, and mitosis) but is absent from resting cells (G0). Because of this, the Ki-67 IHC (Immunohistochemistry) marker serves as a direct indicator of the 'growth fraction' of a given cell population.

Why it is Ordered

In oncology, measuring the rate at which cancer cells divide is crucial for determining the aggressiveness of a tumor. It is most commonly ordered for patients diagnosed with breast cancer, neuroendocrine tumors, lymphomas, and prostate cancer. The Ki-67 index helps clinicians decide between conservative management and aggressive chemotherapy.

Associated Conditions

• Breast Cancer: Used to distinguish between Luminal A (low Ki-67) and Luminal B (high Ki-67) subtypes.
• Neuroendocrine Tumors (NETs): Essential for grading the tumor (Grade 1, 2, or 3).
• Lymphoma: High levels often correlate with more aggressive forms like Burkitt lymphoma.
• Prognostic Value: Generally, a higher Ki-67 index suggests a more aggressive clinical course and potentially a higher responsiveness to chemotherapy, which targets rapidly dividing cells.

Summary

The Ki-67 score provides a snapshot of how many cells in a tumor sample are currently dividing. While it is a powerful tool for prognosis, it is usually interpreted alongside other markers (like HER2 or ER/PR status in breast cancer) to form a complete clinical picture.