Flow cytometric DNA analysis of breast cancers with predominance of carcinoma in situ: a comparison of the premalignant and malignant components.

Flow cytometric DNA analysis was performed on unfixed frozen tissue samples from 48 cases of invasive breast cancer (IC) with a predominance of ductal carcinoma in situ (DCIS). In 15 cases the samples contained only the DCIS component, in 17 cases only the IC component, whereas in 16 cases separate samples from the DCIS as well as the IC part within the individual lesion were available. In the latter 16 cases, complete or partial accordance in DNA ploidy between DCIS and IC was found in 12 cases, whereas no correspondence could be demonstrated in the remaining 4 cases, possibly due to intratumoral DNA heterogeneity. Comparison of the DNA index distribution in samples of DCIS and IC from the 48 cases showed concordant results except for the DNA hyperdiploid subclass, in which 6 clones were found in the DCIS portion compared to 18 clones in the IC portion. S-phase fractions were also comparable in the two groups. A comparison of the DCIS component from the present series of breast cancers to our previous series of pure DCIS also showed similar results with respect to the DNA index distribution, DNA heterogeneity, and S-phase fraction. No differences could be demonstrated between DCIS with and without invasion. The results indicate that the DNA ploidy pattern of breast cancer, as detected by flow cytometric DNA analysis, is established at the preinvasive stage of carcinogenesis.