Long-term tamoxifen therapy may cause:
Long-term tamoxifen therapy is a predisposing factor for endometrial hyperplasia and cancers.
Malignancies caused by Long-term tamoxifen therapy:

Carcinoma endometrium-it is the most common carcinoma associated with it.
Uterine sarcoma.
Rarely liver cancer with a long-term high dose.

Non-malignant effects of tamoxifen on uterus:

Endometrial hyperplasia
Endometriosis
Fibroid uterus
Ovarian cysts
Menstrual irregularities or amenorrhea.
Endometrium Ca
Ovary Ca
Cervix Ca
Vagina Ca