Relationship of cytosolic estrogen and progesterone receptor content and the growth fraction in human mammary carcinomas.

In this study of breast cancer specimens, the relationship between cytosolic estrogen (ER) and progesterone receptor (PR) content to the size of the respective growth fraction (GF) (expressed as percentage of proliferating tumor cells) was investigated. We applied the recently developed ligand-binding assay for extracts of frozen sections and Ki-67 immunocytochemistry for the assessment of the GF to adjoining serial sections of a single tissue block. If the receptor content is plotted against the percentage of Ki-67 labeled cells, an inverse relationship between receptor content and proliferation becomes obvious, meaning that a high receptor content is associated with a small GF and vice versa. If tumor specimens are grouped according to the evaluated receptor status, the mean percentage of Ki-67-positive cells is 12% for ER-positive/PR-positive (ER+/PR+), 26% for ER-positive/PR-negative (ER+/PR-), 55% for ER-negative/PR-positive (ER-/PR+), and 57% for ER-negative/PR-negative (ER-/PR-) specimens. A significant population of tumors exists, however, which exhibit a high receptor content and a high GF. The percentages of ER+/PR+ samples with a high proliferation index are 16 and 26% if the total ER+ population is considered.