Cell proliferation in hyperplastic and in situ carcinoma lesions of the breast estimated by in vivo labeling with bromodeoxyuridine.

The proliferative activity of normal, benign proliferative, and carcinoma in situ (CIS) breast lesions was studied by in vivo labeling with 5-bromodeoxyuridine (BrdU) in 35 patients with concurrent breast carcinoma. The BrdU-labeled cells were identified on histologic sections by an anti-BrdU monoclonal antibody and an immunoperoxidase reaction. The percentage of BrdU-labeled cells in nonatypical hyperplasia (NAH) was higher (1.15 +/- 1.14%) than normal epithelial cells (0.67 +/- 0.56%, p = 0.066, borderline significance). This difference was very significant in postmenopausal women and disappeared in premenopausal women. No significant difference was found in the fraction of proliferating cells between NAH and atypical hyperplasia (AH): 1.15 +/- 1.14% for NAH versus 1.26 +/- 1.19% for AH. In CIS and in invasive carcinoma (ICA), a significant increase in the percent of BrdU-labeled cells was observed when compared to the normal epithelial cells or NAH (p < 0.001). No significant difference was found in the values of BrdU-labeled cells between CIS and ICA (p = 0.29). The percent of BrdU-labeled cells in benign breast lesions, including fibroadenoma, papilloma, and sclerosing adenosis, did not differ from those of the normal epithelial cells. The menopausal status of the patients did not affect the proliferative activity in NAH or CIS. No correlation was found in the fraction of BrdU-labeled cells between the normal and hyperplastic epithelial cells (r2 = 0.012) or between NAH and CIS (r2 = 0.406) or between CIS and ICA (r2 = 0.429).