Correlation of estrogen and progesterone receptors with histologic differentiation in mammary carcinoma

Using a modification of the histologic grading system of the NSABP, we observed a trend towards higher levels of estrogen (E2R) and progesterone receptor (PR) content in well (grade I) and moderately (grade II) differentiated mammary carcinomas. This relationship between receptor content and histologic grade is enhanced by considering estrogen and progesterone receptor simultaneously. The rank correlation between the quantitative levels of E2R and PR was 0.74 among histologic grade I tumors and 0.64 among histologic grade II tumors. Among the grade III carcinomas, the majority of tumors displayed either a paucity of measurable receptor or a divergence between levels of estrogen versus progesterone receptor (r = 0.19). The use of ultrastructural evaluation of features of differentiation is discussed in the evaluation of grade III tumors and in the evaluation of specific histologic types of mammary carcinoma.