Quantitative pathology in uterine smooth muscle tumours: the case for the standard histologic classification criteria

A number of nuclear morphometric factors (longest and shortest axis, perimeter, area, roundness coefficient) as well as the number of mitoses per 20 high power fields with an x40 objective (mitotic index) and the volume corrected mitotic index (VCMI) have been assessed in 33 uterine smooth muscle tumours (14 leiomyomata, 5 leiomyosarcomata, 9 atypical leiomyomata and 5 tumours of uncertain malignant potential). Multivariate analysis showed the VCMI and nuclear roundness coefficient to be the two most significant prognostic factors achieving, by means of Fisher's linear discriminant function, a high percentage of correct reclassification of the tumours into their respective groups. Furthermore, VCMI was shown to be a more accurate prognostic factor than the simple mitotic index. The results uphold the traditional classification histologic criteria and demonstrate the significance of VCMI as a reliable index of mitotic activity.