Evidence that estrogen-receptor-negative, progesterone-receptor-positive breast and ovarian carcinomas contain estrogen receptor.

A small number of primary metastatic breast carcinomas are estrogen-receptor-negative and progesterone-receptor-positive (ER-, PGR+) under the normal ligand-binding assay or sucrose density gradient conditions. Among more than 500 tumors analyzed in this laboratory over a year and a half, 28 cases fit this category, 18 of which were patients 51 years of age or younger (Group A) and 7 were patients over the age of 56 (Group B), The ages of three patients were unknown (Group C). By treatment of each of those tumor cytosols with dextran-coated charcoal before the assay was done, 13 of group A became positive (ER range 10-87 fmol/mg protein); 1 was borderline (ER 3-9 fmol/mg protein); 1 became positive only on sucrose gradient determination, and 2 remained negative. In comparison, two patients in group B shifted from borderline ER to ER+ and only one ER- became ER+ at 10 fmol/mg protein. The data provide additional rationale for determining both ER and PGR in all patients, and have obvious implications for the need of standard methods of determining ER and PGR in the prognosis of women with breast cancer.