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The area provides a reference unit, for example in reference ranges for urine tests. [3]Used for grading of soft tissue tumors: Grading, usually on a scale of I to III, is based on the degree of differentiation, the average number of mitoses per high-power field, cellularity, pleomorphism, and an estimate of the extent of necrosis (presumably a reflection of rate of growth).
An elevated mitotic index indicates more cells are dividing. In cancer cells, the mitotic index may be elevated compared to normal growth of tissues or cellular repair of the site of an injury. [2] The mitotic index is therefore an important prognostic factor predicting both overall survival and response to chemotherapy in most types of cancer ...
Usually the number of mitotic figures is expressed as the total number in a defined number of high power fields, such as 10 mitoses in 10 high power fields. Since the field of vision area can vary considerably between different microscopes, the exact area of the high power fields should be defined in order to compare results from different studies.
In histopathology, the mitosis rate (mitotic count or mitotic index) is an important parameter in various types of tissue samples, for diagnosis as well as to further specify the aggressiveness of tumors. For example, there is routinely a quantification of mitotic count in breast cancer classification. [74]
Note: Mitotic figures are counted only at the periphery of the tumor, and counting should begin in the most mitotically active areas. Mitotic count per 10 high-power fields (HPFs) [ 21 ] Area per HPF
Furthermore, the 2022 WHO classification introduces a two-tiered grading system for medullary thyroid carcinomas based on mitotic count, Ki-67 index and the absence or presence of tumor necrosis. Here, it may be noted that different cut-offs than with tumors of gastrointestinal, aerodigestive and lung origin are applied.
Up to 10-15 mitotic figures per 10 HPF in most active areas. Tongue-like infiltration between muscle bundles of myometrium. May exhibit myxoid, epithelioid and fibrous change. May have foam cells or hyalinization in the stroma.
Hayflick suggested that his results in which normal cells have a limited replicative capacity may have significance for understanding human aging at the cellular level. [ 4 ] It has been reported that the limited replicative capability of human fibroblasts observed in cell culture is far greater than the number of replication events experienced ...