To be honest, this question is out of my range of expertise. None of the people who answer questions here are doctors, but laypeople who answer based on their own experience with RA and whatever knowledge they manage to pick up. However, I can give you a couple of generalities. As you say, hormones do seem to play a role in RA, particularly in terms of increasing decrease of symptoms, but whether they play a role in actually triggering the disease, I don't know. Physical trauma and intense stress are known to be connected to triggering RA in people who have a genetic predisposition for the disease and you could certainly call breast cancer physical trauma with intense stress. Hopefully, your rheumatologist will be able to give you better information.

If you do get a diagnosis of RA, please come back and check out our area for the newly diagnosed for posts on a number of different aspects of living well with the disease. I'd also recommend that you pick up The First Year with Rheumatoid Arthritis - it's an excellent resource and learning tool that can help you get through to a place where you feel more in control. As well, we do have a wonderfully supportive community who will be able to help you through the first tough time, although having survived breast cancer, you already have a whole bunch of coping tools. Don't let the lack of answers to your question discourage you from coming back - it reflects that the community si,ply didn't know how to answer it. Normally, I would have gotten to this question sooner, but I've been off with a shoulder injury and am only slowly working my way through the questions posted in my absence.

One last thing - you may want to check out our Breast Cancer site and try to ask a question in the Q&A section there. It's quite likely that the users in that community may have a better knowledge base about this issue.