Advanced stage and early relapse of breast carcinomas associated with high thymidine labeling indices.

The thymidine labeling index (TLI) showed a lognormal distribution for 133 primary breast carcinomas with a median of 2.21 and a range of 0.04 to 18.6/100. High TLI's were associated significantly with nuclear anaplasia, pushing tumor border, necrosis, cellular inflammation, and total replacement of lymph nodes involved by tumor, and the data suggested an association of high TLI with large primary tumor and the presence of axillary metastasis. Five patients who initially had local or distant spread all had above median TLI's. They and the 38 patients who developed recurrent tumor during a mean interval of 3.2 years of observation after mastectomy showed a higher geometric mean TLI than those who remained tumor-free (2.93 versus 1.85; p less than 0.05). The rate of early relapse for operable patients with above-median TLI's was significantly greater than that for patients with below-median TLI's (p = 0.0018). High TLI appears to be associated with rapid evolution of breast carcinoma both prior to and following diagnosis and treatment.