8 year breast cancer survivor on tamoxifen for 3 years now. transvaginal ultrasound lining 6mm, appears normal and complex. treatment?

Uterine lining 6 mm: Are you post -menopausal? if so 6 mm is a bit on the high side would discuss with gyn endometrial biopsy vs. D&C ( you get more tissue with D&C and can miss a spot since biopsies are usually done blind) or hysterscopic biopsy. Tamoxifen can thicken uterine lining. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5558364/