Comparison of static and flow cytofluorometry for estimation of DNA index and S-phase fraction in fresh and paraffin-embedded breast carcinoma tissue.

DNA index, S-phase and G2/M fractions were measured in breast carcinomas before and after paraffin-embedding. Unfixed tumors were analysed with flow cytometry, while cells prepared from fixed and paraffin-embedded tumors were analysed with both static cytometry and flow cytometry. Cells for static cytometry were prepared with pepsin and cells for flow cytometry were prepared with trypsin. In 44 of 51 paraffin-embedded tumors, analysed with flow cytometry, both DNA index and S-phase fraction could be estimated. There was a strong correlation between the three methods of obtaining DNA indices and S-phase fractions, but this was not true for G2/M fractions. Histograms from flow cytometry of archival material were corrected for background. We conclude that cells prepared from formalin-fixed and paraffin-embedded breast cancer tissue can yield reliable estimation of DNA index and S-phase fraction.