Objective: To define the relative proliferative response and hormone receptors status in ten sites in the mammary gland of surgically postmenopausal cynomolgus macaques given hormone replacement therapy.
Methods: Surgical postmenopausal cynomolgus macaques were given either no treatment (n = 4), conjugated equine estrogens (CEE, n = 4), or combined therapy with CEE and medroxyprogesterone acetate (n = 4). The drugs were administered in the diet, at doses equivalent on a caloric basis to 0.625 mg/woman/day for CEE and 2.5 mg/woman/day for medroxyprogesterone acetate. Immunostaining of mammary sections was done for estrogen receptor, progesterone receptor, and the proliferation marker Ki-67 MIB-1 (MIB). Comparisons were made between central and peripheral gland, by quadrant, left versus right, and with respect to distance from the nipple within each quadrant.
Result: There were no significant differences in hormone receptor or MIB expression within different sites within the gland.
Conclusions: In the surgically postmenopausal, hormone-treated macaque, regional differences in estrogen and progesterone receptors and MIB staining are not apparent. The assumption of homogeneity throughout the gland makes aspiration cytology and multiple biopsy studies feasible in this species.