Mitotic index in evaluation of tumour proliferative activity

Abstract

Tumour mitotic index represents a number of dividing cells per 100 tumour cells. It is the oldest and most frequently used parameter of cell proliferation kinetics in tumours, which is, in addition to numerous immunohistochemical and other markers, still routinely practised as a golden standard. Determination is dependent on urgent tissue fixation, fixative type, manner and procedure of staining, thickness of tissue sections, statistical expression of mitotic count, tissue and microscopic field sampling as well as a counting protocol. When the identical counting techniques are applied, determination of tumour mitotic index becomes an essentially reproductive method. Proposal for routine usage is to express the number of mitotic figures in standard vision area of 2 mm2. Proceeding from minimal variability of mitotic time duration, there were showed a few original formulas which connect mitotic index, acquired by stereological methodology, with differential equation of tumour growth function. In this mathematical way, it is possible to connect structure of the tumour with tumour growth kinetics parameters, for example with potential doubling time. This approach provides growth kinetic examination of once occurring measured human solid tumours, according to their morphology. Tumour mitotic index has been actually applied in classification, biological behaviour prediction, grading, prognosis, evaluation of relapse potential, malignant transformation and metastasis, treatment decision and therapy effect follow-up. In some malignant tumours, such as breast carcinoma, it is an independent prognostic factor.