Effect of tamoxifen on ultrastructure of endometrial carcinoma.

Tamoxifen is a nonsteroidal antiestrogen whose mode of action is, as yet, unclear. The purpose of this report is to investigate the effects of Tamoxifen on endometrial adenocarcinoma ultrastructurally. Five patients with endometrial adenocarcinoma, 3 cases well differentiated and the others undifferentiated, were treated with 20mg Tamoxifen per os a day for 7 days, and the following changes were observed: The cells became roundish and slightly swollen. Development of cytoplasmic organelles was observed. In the cytoplasm, glycogen granules did not increase. These results suggest that an anti-cancer effect is brought about by the induction of the tissue toward functional differentiation as well as inhibition of glycogen metabolism in tumor cells.