Standardized mitotic counts in breast cancer. Evaluation of the method.

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 of 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 of 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 of the mitotic counts in grading (the grading efficiency) was used to evaluate the mitotic counts. In 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% of the cases correctly) than in the group specially trained for the purpose (trained technicians had the potential to grade 95% of the cases correctly). Among the specially trained technicians, the grading efficiency was of 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 of determining proliferative activity in breast cancer.

Prognostic value of morphometry and DNA flow-cytometry features of invasive breast cancers detected by population screening: comparison with control group of hospital patients.

Using the prognostic value of morphometric and flow-cytometric features, a group of patients with invasive breast cancers detected with population screening (PS, n = 70) has been evaluated and compared with a random control group in 2 hospitals (H group, n = 225) diagnosed in the same period. The results show that the PS patients had smaller tumors, less positive lymph nodes, better differentiated tumors with a lower mitotic activity index (MAI) and lower values of the morphometric prognostic index (MPI). Furthermore, the women more frequently had diploid tumors and tumors with small nuclei. The second purpose was to evaluate whether quantitative microscopical features, in comparison with other prognostic features such as size of primary tumor, nodal status and histologic grade, are as strong prognosticators in PS tumors as in H-detected breast cancers. In comparison with H tumors, morphometric and flow-cytometric features, as well as tumor size, had the same prognostic value for the PS tumors. In contrast, nodal status was not significant within the PS group, and the same phenomenon was found in a subgroup of H patients with similar sized tumors. Of all quantitative microscopical features (MPI, MAI, mean nuclear area (MNA) and DNA Index (DI], the MAI had the strongest prognostic value. DI showed additional prognostic value to the MAI for patients with small tumors and with small tumor-cell nuclei, because a diploid pattern in these cases (this combination occurred in 21 patients of the total group = 30%) was correlated with a 95% 10-year survival rate. Histologic grade, although significant within the large H group, was of no prognostic value within the PS group, and also not as in the H sub-group with small tumors. It is concluded from morphometric and DNA flow-cytometric criteria that these prognostic features in invasive breast cancers detected by PS were all more favorable than in randomly detected hospital breast cancers. This may account for the reported better survival rate of PS patients. Furthermore, the prognosis of patients with small invasive breast cancers detected by population screening can be more accurately deduced by quantitative microscopical features than by axillary-lymph-node status.

Further evaluation of the prognostic value of morphometric and flow cytometric parameters in breast-cancer patients with long follow-up.

The added prognostic value of cellular DNA content compared with single and combined morphometric factors and classical parameters such as tumor size, nodal status, histologic grade and estrogen receptor (ER) content was investigated in 225 consecutive breast-cancer patients with long follow-up. Of all features investigated, the MPI (multivariate prognostic index) had the strongest prognostic value [Mantel-Cox (MC) = 48.2, p less than 0.00005]. The results further showed that neither age nor ER content had significant prognostic value, but the DNA index (DI) as a single parameter had (though weak) prognostic significance (MC = 5.9, p = 0.015); a similar result was obtained with the percentage of S-phase cells (MC = 6.1, p = 0.013). The DI had (restricted) additional prognostic value to the morphometric features (MPI plus DI Mantel-Cox 53.0, p less than 0.0001). The percentage of S-phase cells had no additional prognostic value over the MPI. On the other hand, the additional value of the DI over tumor size and nodal status was much more impressive (MC = 41.0 and 40.7), although it did not reach the prognostic significance of the MPI. Prediction of disease outcome with a linear combination of quantitative microscopical parameters of the primary tumor alone [MAI (mitotic activity index), DI and mean nuclear area] was very accurate, even without considering lymph-node status (MC 30.8, p less than 0.0005). Grade had no additional value to the MPI at all (p = 0.76). This could be especially important for lymph-node-negative patients in whom the prognostic value of the MPI and the MAI are confirmed.

Limited prognostic value of cellular DNA content to classical and morphometrical parameters in invasive ductal breast cancer.

This retrospective study evaluates several prognostic factors in 63 patients with invasive ductal breast cancer. Special attention is paid to the additional prognostic value of cellular DNA content to the previously developed and evaluated quantitative features mitotic activity index (MAI) and multivariate morphometric prognostic index (MPI). Follow-up was monitored for at least 50 months (median survival, 78 months) and only patients who died of distant metastases were included. The results show that the MAI is the strongest prognostic factor of all single features (Mantel-Cox, P = 0.008). Although patients with a diploid or tetraploid tumor tended to have a better prognosis than those with an aneuploid cancer, the DNA index as a single parameter was a weak prognosticator in the univariate survival analysis (Mantel-Cox, P = 0.24). Within the diploid and tetraploid tumors the MAI could distinguish patients with a favorable and unfavorable prognosis prediction (chi-square, P = 0.01). For aneuploid tumors this was not possible. Analysis of combined features revealed that the MPI has a high prognostic value (Mantel-Cox, P = 0.0015), thus confirming other studies. A linear combination of the nuclear DNA index, MAI, nodal status, and mean nuclear area showed only a slight improvement in prognosis prediction compared with the MPI (Mantel-Cox, P = 0.0005); with this rule, the classification of the patients was more in agreement with the actual outcome in 4% of the cases. The gain was in the poor prognosis group. These results suggest that the additional prognostic value of nuclear DNA content is restricted when compared with the morphometric prognostic factors. Further studies on a larger number of patients are required to confirm these findings.