Ki-67

Ki‑67 is a nuclear proliferation marker expressed during all active phases of the cell cycle (G1, S, G2, and M) but absent in resting (G0) cells. In IHC, it is nuclear stain and is widely used to assess tumour proliferative activity, helping distinguish benign from malignant lesions and contributing to grading in tumours such as neuroendocrine neoplasms, pituitary tumours, sarcomas, and meningiomas. The percentage of Ki‑67 positive tumour nuclei (the Ki‑67 index) provides important prognostic information in cancers including breast, bladder, prostate, and chordoma. Cytoplasmic staining is disregarded, and evaluation typically focuses on positive regions with the highest density of proliferating cells (1).

Recommended Controls

Criteria for acceptable staining is a nuclear staining pattern. Recommended control is tonsil, strong positive staining will be seen in the in the dark zones of the B-cells germinal centers, weak staining in the light zones of the B-cells and no staining should be seen in the mantle zone B-cells.

Expected staining pattern

Tonsil (1)

Tonsil (2)

Disclaimer

These methods are intended as a guide only. Laboratories that wish to implement these methods should perform internal validation/verification prior to use. The RCPAQAP does not make any claim or warranty for the accuracy or performance of these methods.