Molecular markers in the endometrium at baseline of postmenopausal patients with early breast cancer in the ATAC (Arimidex, tamoxifen, alone, or in combination) trial.

Objective: This study was undertaken to assess baseline endometrial molecular events in the ATAC (Arimidex, tamoxifen, alone, or in combination) trial of breast cancer adjuvant therapy.

Study Design: Estrogen receptor (ER) and progesterone receptor (PR) levels and markers of cell proliferation (Ki67) and apoptosis ( Bcl -2) were assessed in 93 patients at baseline.

Results: An inactive/atrophic endometrium was found in 63 patients, 5 had a proliferative endometrium, and 12 had a secretory endometrium. Thirteen endometrial polyps were analyzed. Inactive endometrium showed high levels of ER in the glandular epithelium, whereas in more than 50% of samples, PR expression was negative or low (+) in the glandular epithelium, and stroma. Ki67 expression was low in both the glandular epithelium and the stroma of the inactive endometrium, whereas Bcl -2 expression was mostly high or very high (+++/++++) in the glandular epithelium. Bcl -2 was strongly expressed (+++/++++) in the glandular epithelium of polyps.

Conclusion: Although all patients were asymptomatic, some had endometrial pathology.