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Mitotic index is defined as the ratio between the number of cells in a population undergoing mitosis to the number of cells in a population not undergoing mitosis.
The purpose of the mitotic index is to measure cellular proliferation. The mitotic index is an important prognostic factor predicting both overall survival and response to chemotherapy in most types of cancer. It may lose much of its predictive value for elderly populations. For example, a low mitotic index loses any prognostic value for women over 70 years old with breast cancer.
Additionally, the mitotic index is simply a measurement to determine the percentage of cells undergoing mitosis. Mitosis is the division of somatic cells when genetic information from one single cell is equally dispersed into two daughter cells. Durations of the cell cycle and mitosis vary in different cell types. An elevated mitotic index indicates more cells are dividing, and thus obvious in cancer cells, The mitotic index may be elevated during necessary processes to life, such as the normal growth of plants or animals, as well as cellular repair the site of an injury.
Mitotic index can be calculated using the following operation : cells observed with visible chromosomes ÷ total number of cells visible.
A typical figure of mitotic index includes statements like "10 mitotic figures are noted per 10 high power fields" followed by "4 mitotic figures noted per 50 high power fields". Mitotic index: 14 MF/10 400x fields
, (P+M+A+T) — the sum of all cells in phase as prophase, metaphase, anaphase and telophase, respectively; N — total number of cells.
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