Mammary carcinoma: DNA analysis in areas showing different histological features in the same tumor

Specimens from 17 invasive primary breast adenocarcinomas that showed distinct areas of different histologic appearance were examined with respects to nuclear DNA content of the tumor cells. DNA in individual tumor cells was measured in sections from the original paraffin-embedded specimens. DNA distribution patterns obtained from the histologically different areas in the same tumor were compared. In 15 cases these patterns were very similar, whereas in two cases the patterns were found to be different. The results suggest that, in spite of histological variations, breast carcinoma often show similar nuclear DNA content throughout the entire tumor. Since nuclear DNA content in breast tumors has been shown to be correlated to prognosis, our observations suggest that the differences in structural pattern occasionally seen in mammary adenocarcinoma do not necessarily reflect a dedifferentiation towards more malignant tumor populations.