In vitro bromodeoxyuridine labeling of malignant neoplasms. A comparative study with flow cytometry cell-cycle analysis.

Proliferative fraction has been defined as an independent prognostic marker for some malignant neoplasms. An estimate of the proliferative fraction can be obtained by cell-cycle analysis of flow cytometric DNA measurements. However, overlapping DNA distributions of aneuploid neoplasms are difficult to analyze, even with sophisticated computer programs, and results are not always reproducible. Bromodeoxyuridine (BrdUrd) labeling followed by immunohistochemical detection has been proposed as an alternative, simple, and accurate method for identifying and counting DNA synthesizing cells. In vitro BrdUrd labeling was performed on 87 tumors, including 35 lung cancers, 25 breast carcinomas, and 27 tumors of other origin. Results were compared with flow cytometric S-phase estimates in 46 cases. Mean BrdUrd labeling of lung tumors was 8.5% +/- 5.2%, compared with a mean flow cytometric S-phase fraction of 20% +/- 18.4%. Mean BrdUrd labeling of breast carcinomas was 6.8% +/- 3.8%, compared with a mean flow cytometric S-phase fraction of 12.5% +/- 9.9%. In both tumor types, BrdUrd labeling correlated well with histologic grade. Correlation between BrdUrd labeling and flow cytometric S-phase estimates were generally poor, particularly with aneuploid tumors.