To investigate whether breast cancer cells with unusually high nuclear DNA content are associated with an adverse outcome, Eastern Cooperative Oncology Group investigators selected breast cancer trial patients who suffered an early death (ED) within two years after diagnosis to compare with other trial patients who had a survival of at least 7.5 years. Paraffin blocks of primary breast cancers were obtained from 93 evaluable patients who had been enrolled in two surgical adjuvant trials for lymph node positive (LN+) disease (T1-3N1M0). Single cell monolayer preparations from these blocks were stained with acriflavine-Feulgen and analyzed by image analysis for DNA content with the automated Leiden Television Analysis System (LEY-TAS). Standard prognostic variables (estrogen receptor (ER) status, number of lymph nodes with metastases, and size of the cancer) were compared with three DNA content characteristics: DNA ploidy status, number of nuclei with > 5C DNA content, and percent of nuclei with > 5 C. Estimates of the odds ratio in multivariate comparisons showed that ER negativity was associated with ED (p = 0.0005) and an odds ratio estimate using negative/positive of 4.87. The number of positive lymph nodes associated with ED had a p-value of 0.0005 and an odds ratio estimate of 4.63 when comparing the > 3 nodes group to the 1-3 nodes group. In contrast, the strongest association for any of the DNA content characteristics with ED had a p-value of 0.017 and an odds ratio estimate of 2.76. This power of association disappeared when stratified on ER status.(ABSTRACT TRUNCATED AT 250 WORDS)