Intratumoral heterogeneity of DNA ploidy in breast carcinomas: a flow cytometric assessment of sampling techniques

Intratumoral heterogeneity of DNA ploidy has been identified in breast carcinomas; however, optimal sampling methods have not been determined. In this study of 28 invasive breast carcinomas measuring more than 1.4 cm in greatest dimension, two different techniques for obtaining cells for flow cytometric DNA ploidy analysis were compared. Two solid pieces of tissue were taken from opposite halves of the tumor. A third sample was obtained by scraping multiple cut surfaces of the tumor. Heterogeneity of DNA ploidy was detected in 43% of cases. Most cases demonstrating heterogeneity contained multiple aneuploid populations. However, in five cases classification of the tumors as either DNA euploid or DNA aneuploid differed among samples. A total of 39 non-diploid populations were detected in 23 of the cases. Thirty-three (85%) were detected by scraping and 35 (90%) were detected in either one or both tissue pieces. Intratumoral DNA heterogeneity emphasizes the need for adequate sampling. The scraping technique was as effective in identifying aneuploid cell populations as the combined results of the two pieces of tissue and better than sampling a single piece of tissue. Scraping also offers the advantage of tissue conservation which may be critical when various analytic studies are performed.