Human breast cancer: heterogeneity of estrogen binding sites.

A patient who had two primary tumors in the same breast is described. Both tumors were infiltrating duct carcinomas, but they differed as far as histologic malignancy and estrogen-receptor-positivity are concerned. One tumor was estrogen-receptor-positive the other was estrogen-receptor-negative. The case illustrates the multicentric origin of breast cancer as well as its cellular heterogeneity. Problems of treatment are discussed.