Volume corrected mitotic index (M/V index), mitotic activity index (MAI), and histological grading in breast cancer

A prospective study on breast cancer was started in 1975, and ended in 1987 allowing a mean follow-up of 12.4 years. At the operation tumor size was registered, and after axillary evacuation axillary status was defined histologically. In 1989-1990 volume corrected mitotic index (M/V index), and mitotic activity index (MAI) were estimated, and histological grading performed from archival paraffin sections. In univariate survival analysis axillary node status (p less than 0.0001), M/V index (p less than 0.0001), MAI (p = 0.0001), and tumor size (p = 0.0009), histological grade (p = 0.0195), and irregularity of nuclei (p = 0.0167) predicted survival, recurrence free survival, and breast cancer survival. In a multivariate survival analysis axillary node status, M/V index, tumor size and tubular growth pattern showed independent prognostic value in the order of significance. In the separate analysis of infiltrative ductal or lobular carcinomas the M/V index was the most important prognosticator. The results suggest that the M/V index is more powerful in predicting survival than the mitotic activity index (MAI) in breast cancer. Obviously this is due to better control of variation factors associated with field size and area of epithelium by the M/V index.