Hi Loubel, I have been on tamoxifen about 2 years and am pre-menopausal. I stopped bleeding altogether on tamoxifen and then started again just a little. Was referred for ultrasound because as you say tamoxifen can have endometrial cancer as a SE and I think they want to be careful. Scan showed thickening so I ended up having an investigation (called a hysteroscopy where they check with a little camera and a biopsy. I didn't have a polyp - which as best as I know are benign but can cause bleeding? My SiL had one, nothing to do with bc - but had I had, It would have been removed in the same procedure and checked. There was another woman who'd had bc there at the same time as me and that is what she was doing, having a polyp checked out.
It is a ten minute procedure and I was told that it is VERY rare to get endometrial C, they just want to be vigilant. I guess I am glad that they do, even though scans and waiting for results is so scary. I know of a few other people who have had similar issues on tamoxifen or other hormone treatments so I don't think it's that uncommon xx