Age and incidence of estrogen receptor positive breast tumors.

Estrogen receptors of primary breast cancer tumors were determined by sedimentation analysis. Positive tumors from pre- and post-menopausal patients were those that contained estrogen receptor content greater than 250 and greater than 750 fmoles per g wet weight tissue, respectively. A positive correlation of patients' age with increasing incidence of estrogen receptor positive tumors was found; test for linear trend significance z = 5.38 (P less than 0.001). One-sixth of those less than 29 years had positive tumors, 27 percent in the age group 40 to 49 years, 46 percent in those 70 to 79 years, and 62 percent in those 80 years or older.