Ki-67 index is mainly relevant in those with stage T1-T2, N0-N1, to determine if chemotherapy is needed (if Ki67 is >30% rather than <5%).[1]
Ki-67 index is most feasibly quantified by a hot spot method,[note 1] Hot spots are areas in which Ki-67 staining is particularly higher relative to the adjacent tumor areas.[2] Usually, the invasive edge of a tumor is a hot spot.[2] When a tumor had several hot spots, the “hottest” spot is selected.[2] Aim to count at least 500 cells in each case, but this is not always possible in cases with low tumor cell density and small tumor size.[2] Also aim to include at least three high-power (×40 objective) fields. Count a nucleus as “positive” if there is any definite brown staining in the nucleus of an invasive breast cancer cell, above the surrounding background in the cytoplasm and extracellular matrix.[3] If a comparisons must be made between core biopsies and sections from an excision, evaluation of the latter should be across the whole tumor.[1] Only nuclear staining counts. Staining intensity of a positive nucleus is not relevant.[1]
HER2 can also be evaluated by fluorescence in situ hybridization (FISH), either initially or in case of borderline/equivocal immunohistochemistry.[8] It usually uses chromosome enumeration probe 17 (CEP17) to count the amount of chromosomes, the HER2/CEP17 ratio reflects any amplification of HER2 as compared to the number of chromosomes.
Classification of HER2 by fluorescence in situ hybridization (FISH)[9]
HER2/CEP17 ratio
≥2.0
<2.0
Average HER2 copy number per cell
≥4.0
HER2 positive
Additional work-up requiredCite error: Closing </ref> missing for <ref> tag
In breast cancer metastases, retest estrogen and progesterone receptors, and HER2 in the following circumstances:[10]
If the status of the primary tumor is unknown or negative for ER/PR and/or HER2
If the primary tumor is heterogeneous for ER/PR expression
If the metastatic progression is unusual for the tumor characteristics
If the relapse is unexpectedly early or late
If unusual metastasis location
If the initial test was performed more than 10 years ago
If the testing turnaround time are relatively short (to reduce potential delays in patient management by retesting)
Notes
↑Besides from a hot spot method of Ki67 counting, there is also a IKWG global average method which is more comprehensive. However, the inter-observer difference between the hot spot method and the 'IKWG global average is not statistically significant, and has not shown any significant difference in clinical outcome (theoretically, the area of highest Ki-67 proliferative index is probably most likely to correlate with malignant transformation and risk of metastasis, making the hot spot both more straightforward and clinically relevant than a global average). - Reference and instructions for the IKWG global average method: Dowsett, M.; Nielsen, T. O.; A'Hern, R.; Bartlett, J.; Coombes, R. C.; Cuzick, J.; Ellis, M.; Henry, N. L.; et al. (2011). "Assessment of Ki67 in Breast Cancer: Recommendations from the International Ki67 in Breast Cancer Working Group
". JNCI Journal of the National Cancer Institute103 (22): 1656–1664. doi:10.1093/jnci/djr393. ISSN0027-8874.
↑ 1.01.11.2Dowsett, M.; Nielsen, T. O.; A'Hern, R.; Bartlett, J.; Coombes, R. C.; Cuzick, J.; Ellis, M.; Henry, N. L.; et al. (2011). "Assessment of Ki67 in Breast Cancer: Recommendations from the International Ki67 in Breast Cancer Working Group
". JNCI Journal of the National Cancer Institute103 (22): 1656–1664. doi:10.1093/jnci/djr393. ISSN0027-8874.
↑ 2.02.12.22.3Coleman, William B.; Jang, Min Hye; Kim, Hyun Jung; Chung, Yul Ri; Lee, Yangkyu; Park, So Yeon (2017). "A comparison of Ki-67 counting methods in luminal Breast Cancer: The Average Method vs. the Hot Spot Method
". PLOS ONE12 (2): e0172031. doi:10.1371/journal.pone.0172031. ISSN1932-6203.
