Does taking tamoxifen for breast cancer treatment induce cancer of the womb?

Small risk: Tamoxifen is asociated with a small (less than 5%) risk of uterine cancers, women on tamoxifen require regular gynecologic checkups every 6-12 months and high-risk women may need ultrasound screeenings too.

Possible but rare: Uterine wall thickening is a known side effect of tam. It usually presents as abnormal spotting or bleeding. Definitive DX is via endometrial biopsy. If ignored it can progress to uterine cancer. This is usually cured with hysterectomy alone.