Receptor heterogeneity of human breast cancer as measured by multiple intratumoral assays of estrogen and progesterone receptor

Multiple intratumoral tissue samples from the primary mass of 30 consecutive invasive breast cancer patients were assayed for estrogen receptor (ER) and progesterone receptor (PR) by the dextran-coated charcoal method following frozen section histopathological examination. Steroid receptor status of each sample was classified as positive (R+) or negative (R-), based only upon quantitative guide lines form the ER/PR results. Four out of 32 (12.5%) of the invasive cancers had an intratumoral sample classified as R+ and one sample as R-. R+ invasive ductal carcinomas has a highly significant degree of tubule formation (P = 0.005) when compared with R- invasive ductal cancers. While the quantitative ER content (r = 0.18) and the degree of quantitative variation in ER content (P = 0.04) did not correlate with the tumor cellularity of the individual samples, tumor cellularity (P = 0.005) and ER content (P = 0.005) were lower in the samples from the tumor border than from the central tumor samples. Variations in ER and PR content may be found on a regional basis within a breast tumor mass resulting from heterogeneity of tumor subpopulations and/or differences in tumor cellularity.