Abstract
The frequency distribution curve of the erythrocyte sedimentation rates obtained from a population of 3523 normal females was compared with the distribution found in 544 patients with benign breast disease and that for 385 patients with carcinoma of the breast. No significant difference was found between the normal female population and patients with benign lesions of the breast. This was in contrast to the distorted distribution curve of erythrocyte sedimentation rates exhibited by the population of patients having malignant breast lesions. An unknown substance present in the blood plasma of the cancer patients appears to be responsible for the abnormal sedimentation rate phenomenon.