Twenty-five human breast cancers, surgically resected, were studied by cytogenetic analysis and DNA flow cytometry (FCM). The establishment of karyotypes showed that multiple cell populations probably were derived from a single ancestor clone, because common marker chromosomes always could be demonstrated. Differences of up to 30% were observed when the estimates of DNA content by the two methods were compared. A general tendency toward the acquisition of large marker chromosomes should be at the origin of this discordance, as the proportion Cytogenetic (CGj analysis has proved to be a powerful tool for studying chromosomal abnormalities in human malignancy (37,46). A number of primary events thus have been characterized, some of which are tumor-type specific. However, it is a long and painstaking method and even in expert hands, is successful only for a limited number of samples. DNA modal values first were estimated on interphase nuclei by static cytophotometry, which showed frequent deviations as compared with the content of normal diploid cells and which introduced the prognostic significance of this parameter (3,4,41). The development of several methods for obtaining DNA histograms from solid tumors by flow cytometry (FCM) has facilitated the study of a large number of samples (9,30,42,44). The application of DNA-FCM on archival material (18) has extended the possibilities by permitting retrospective studies with a long follow-up (10,17,19). However, results have shown considerable variability, often within a specific cancer, but also between the different tumor types. Furthermore, if aneuploidy has been generally recognized as indicative of a poor prognosis, it has been shown to have favorable incidence on outcome in childhood acute leukemia (26).Studies comparing CG and FCM results, on various tumor types have shown the existence of discordant cases on the basis of DNA content (2,32,43). We have of markers for each case correlated significantly with the magnitude of the difference. Parallel use of the two methods revealed the existence of tumors with DNA diploid FCM profiles and highly abnormal hypodiploid karyotypes (35-40 chromosomes), which may explain the limited value of DNA ploidy as an independent prognostic factor in breast cancer.Key terms: Human breast cancer, DNA ploidy, cytogenetics, prognostic value shown previously that quantitative measurements of DNA (chromosome counts and DNA indices) are highly correlated in colorectal cancers (34).We are reporting here our CG and FCM results for 25 cases of human breast cancer. Chromosome banding has been used systematically for karyotypic analysis to obtain more qualitative information at the genetic level, as compared with DNA histograms. Implications as to the possible value of DNA index in terms of prognosis are discussed.
MATERIALS AND METHODSNinety-four surgical specimens of previously untreated breast cancer were sent by pathologists to the cytogenetics department, 32 of which (34%) produced sufficient analyzable metaphases (4-41). FCM DNA histog...