Endometrial biopsy

I had breast cancer 1 year ago and have been on Tamoxifen.  My pelvic US showed abnormal thickening of the endometrial lining.  Dr. tried to do a biopsy in the office but couldn't because of cervical stenosis (I had cervical cancer 20 years ago).  Went to hospital and had an D & C and hysteroscopy in Sept. but this was unsuccessful and Dr. didn't get to the tissue for a biopsy.  Went back last week to have it done again and Dr. did a LEEP procedure.  I just found out that this too was unsuccessful.  Dr. doesn't know what to do other than a hysterectomy.  I have no symptoms and don't understand why Dr. couldn't get a biopsy even after a LEEP?  Has anyone had anything like this?