Mitosis–Karyorrhexis Index
Pronunciation: kar-ee-oh-REK-sis
Also written as: MKI — Mitosis–Karyorrhexis Index
A quantitative histological measure in neuroblastoma pathology counting the combined number of mitotic figures and karyorrhectic cells per 5,000 tumour cells, used to assign favourable or unfavourable histology.
Full Definition
The mitosis–karyorrhexis index (MKI) is calculated by counting all cells in active mitosis and all cells showing karyorrhexis (nuclear fragmentation as a marker of apoptosis) in 5,000 consecutively examined neuroblastic tumour cells on haematoxylin-and-eosin stained sections. MKI categories are: low (<100/5,000; <2%), intermediate (100–200/5,000; 2–4%), and high (>200/5,000; >4%). Together with patient age and tumour differentiation, MKI is a core input into the INPC to determine histological category. Editors should ensure MKI is expressed as both a ratio and percentage in pathology reports, and that the correct MKI category label (not a numeric value alone) is present, as the categorical designation drives downstream treatment decisions.
Usage
Usage note: MKI should be distinguished from the general mitotic index (mitoses only) and from Ki-67 proliferation index; all three measure proliferation by different methods and are not interchangeable in neuroblastoma reporting.
In Context
- "The mitosis–karyorrhexis index was calculated at 3.2% (intermediate), contributing to an unfavourable histology classification for this 18-month-old patient." — Pediatric oncology pathology report
- "The report cited only the numeric MKI value without the categorical label; the editor requested the low/intermediate/high designation be added." — Quality-assurance review