For postmenopausal women, why is it dangerous to go back on estrogen patch after being off it for 3 years (unopposed estrogen patch, tiny dose)?

Controversy: Recent keeps study suggests timing is key to use of estrogen/progesterone in menopause. Even a tiny dose of unopposed estrogen is not recommended if you still have your uterus (did not have hysterectomy) since this can/will increase risk of uterine cancer. Progesterone protects against this. Evidence is clear that estrogen doesn't help prevent much if you start 10yrs post-menopause. You're inbtwn.