Standardized Mitotic Counts in Breast Cancer Evaluation of the Method

• Published in: Pathology, research and practice research and practice, 1996-09, Vol.192 (9), p.931-941
• Main Authors: Collan, Y.U.I., Kuopio, T., Baak, J.P.A., Becker, R., Bogomoletz, W.V., Deverell, M., Van Diest, P., Van Galen, C., Gilchrist, K., Javed, A., Kosma, V.-M., Kujari, H., Luzi, P., Mariuzzi, G.M., Matze, E., Montironi, R., Scarpelli, M., Sierra, D., Sisti, S., Toikkanen, S., Tosi, P., Whimster, W.F., Wisse, E.
• Format: Article
• Language: English
• Subjects: Breast cancer; Breast Neoplasms - pathology; Grading efficiency; Humans; M/Vv index; MAI; Mitotic Index - genetics; Observer Variation; Pathology, Surgical - standards; Proliferative activity; Reference Standards; SMI; Standardized mitotic index
• ISSN: 0344-0338; 1618-0631
• DOI: 10.1016/S0344-0338(96)80075-6

Twenty-one pathologists and technicians participated in a study evaluating the variation present in mitotic counts for prognostication of breast cancer. The participants counted the mitotic figures in 20 breast cancer samples from ten high power fields (mitotic activity index, MAI, giving the results in mitotic figures per 10 fields) and also made a correction for field size and area fraction o f the neoplastic epithelium to get the standardized mitotic index (volume fraction corrected mitotic index, or M/Vv index, giving the result in mitotic figures per square mm o f neoplastic epithelium). The difference in variation between the two methods was not big, but the standardized mitotic index (SMI) showed consistently smaller variation among all participants and different subgroups. Experienced pathologists had the highest variation in mitotic counts, and specially trained technicians, the lowest. The efficiency o f the mitotic counts in grading (the grading efficiency) was used to evaluate the mitotic counts. I n groups without special training for mitotic counts the mean grading efficiency was lower (experienced and training pathologists both on average had the potential to grade 88% o f the cases correctly) than in the group specially trained for the purpose (trained technicians had the potential to grade 9S% o f the cases correctly). Among the specially trained technicians, the grading efficiency was o f the same magnitude as the grading efficiency achieved in determining the S-Phase fraction of cells from paraffin embedded breast cancers by flow cytometry in different laboratories. The results suggest that special training is helpful in making mitotic counts more reproducible, and that in trained hands, the mitotic counts give results comparable to more sophisticated methods o f determining proli ferative activity in breast cancer.