Over a 40-year period at one hospital, 3,426 operative specimens of primary breast cancer were seen and analyzed for the maximum diameter of the primary cancer and the number of metastatic axillary lymph nodes. Statistically, significant trends toward progressively smaller primary cancers and fewer axillary metastases have been recorded, particularly over the 20 years ending in 1968. Currently, the median maximum diameter of primary breast cancer is 2.5 cm, and the mean maximum diameter is 3.07 cm. Fifty-three percent of all specimens now have negative axillary lymph nodes, and of those with positive axillary lymph nodes, 31% have one metastatic node, 14% have two metastatic nodes, and 13% have three metastatic nodes.
Cady B. Changing Patterns of Breast Cancer. Arch Surg. 1972;104(3):266-269. doi:10.1001/archsurg.1972.04180030014006