DNA content flow cytometry as a prognostic factor for node‐positive breast cancer. The role of multiparameter ploidy analysis and specimen sonication

The DNA content was analyzed in paraffin‐embedded material from 167 patients with node‐positive breast cancer to learn whether specimen sonication and multiparameter ploidy analysis (MPPA) (using DNA content and light scatter) could improve the strength of ploidy as a prognostic variable. Sonicated specimens were found to have fewer aggregates, a lower percentage of cells in S‐phase (%S) and G2M phase than the corresponding nonsonicated specimens. The results using MPPA predicted the prognosis better because they allowed detection of small aneuploid peaks in histograms classified as diploid or tetraploid using DNA content alone. Ploidy was a significant univariate factor, and patients with tetraploid tumors had the best survival. In the multivariate analysis, if other routine factors were examined preferentially, ploidy and %S did not provide additional prognostic information for survival. This study of paraffin‐embedded breast cancers suggested that sonication and MPPA may improve the ploidy analysis in certain cases and that tetraploidy may be a favorable ploidy pattern in this group.