Cell kinetics of histologic variants of in situ breast carcinoma

A thymidine labeling study of cell kinetics of 61 in situ breast carcinomas showed relationships between histological characteristics and kinetics. The thymidine labeling index (TLI) was significantly lower in cribriform-papillary intraductal carcinoma (median 1.30%, geometric mean 1.18%, mean 1.83 +/- 0.45%) and lobular carcinoma in situ (median 1.43%, geometric mean 1.12%, mean 1.63 +/- 0.46%) than in comedo intraductal carcinoma (median 4.40%, geometric mean 3.74%, mean 5.15 +/- 0.86%). The results for solid intraductal carcinoma, which is a less well defined and more heterogeneous entity, were intermediate (median 2.45%, geometric mean 2.40%, mean 3.32 +/- 0.80%). When invasive carcinoma was also available for kinetic study, the TLI of in situ and invasive components were usually similar (r = 0.66). The data indicate that the TLI usually does not change during the transition from in situ to invasive carcinoma. Cribriform-papillary intraductal carcinoma is a slowly proliferating entity that gives rise to slowly proliferating invasive carcinomas with relatively high levels of estrogen and progesterone receptors. Lobular carcinoma in situ similarly has low proliferative rates and gives rise to slowly proliferating invasive carcinomas. Intraductal comedocarcinoma has relatively high proliferative rates and gives rise to invasive carcinomas with high proliferative rates that often are receptor-negative. Nine of the 11 in situ carcinomas that were associated with invasive tumor and subsequent local recurrence or metastasis had TLIs above the median, and seven were comedo type with high TLIs. Our observations from thymidine labeling are consistent with a viewpoint regarding cribriform-papillary intraductal carcinoma as relatively bland, and comedo intraductal carcinoma as a distinctly more dangerous entity. Solid intraductal carcinoma seems to resemble cribriform-papillary more closely than comedo intraductal carcinoma.