Would you discontinue tamoxifen for endometrial hyperplasia without dysplasia in the adjuvant setting?  

I would not. Endometrial hyperplasia is to be expected on tamoxifen, especially in a postmenopausal woman. It is not recommended to do a transvaginal ultrasound or endometrial biopsy without suspicion of tamoxifen. I would not change therapy in the absence of other suspicious findings.