Biochemical correlates of morphologic differentiation in human breast cancer.

In 115 breast carcinoma tissues, histologica grade and cell cytosol concentrations of estrogen receptor (ER) and progesterone receptor (PR) and two breast cyst fluid proteins (gross cystic disease fluid protein [GCDFP-15] and nonreceptor progesterone-binding protein [PBP]) were deterMined. Higher levels (expressed as femtomoles per milligram of protein) of ER (128 +/- 28 versus 11 +/- 1, P less than 0.001) and PR (82 +/- 16 versus 3 +/- 1, P less than 0.001) were found in grade 1 (well-differentiated) carcinomas as compared with grade 3 (poorly differentiated) carcinomas. Similarly, higher concentrations (expressed as nanograms per milligram of cytosol protein) of GCDFP-15 (2110 +/- 840 versus 210 +/- 40, p less than 0.001) and PBP (4920 +/- 1200 versus 370 +/- 60, P less than 0.001) were found in grade 1 as compared with grade 3 carcinomas. Tumor cytosols that contained low levels of both cyst proteins (less than 225 ng/mg GCDFP-15 and less than 750 ng/mg PBP) had a high incidence of grade 3 (35 of 46, 78%) or grade 2 (15 of 46, 33%) histologic findings and had a high incidence of receptor-negative specimens (27 of 52, 52%). Based on these cutoff levels, grade 2 lesions were subdivided into a "high" cyst protein group, which had ER and PR levels similar to grade 1 tumors (93.1 +/- 26.7 for ER and 84.7 +/- 32.4 for PR, P greater than 0.3), and a "low" group, which had receptor values similar to grade 3 carcinomas (14.1 +/- 5.3 for ER and 9.1 +/- 5.2 for PR, P less than 0.3). Although the mean cytosol content of carcinoembryonic antigen (CEA) was significantly higher in malignant tissues (125 +/- 27 ng/mg cytosol protein) than in benign tissues (4.8 +/- 1 ng/mg cytosol protein), the CEA content was not significantly different between grades 1 and 3 tumors.