Unsure, From what I've read the discomfort caused by a thymoma would be due to pressure from a large tumor pressing against heart/lungs etc. If you had a large tumor they would have seen that. Thymomas are rare and can go undetected until they are quite large. That can cause them to be undiagnosed until a late stage malignancy has been reached. It doesn't seem like pain in the front of your chest would be due to a thymoma, especially since you had an xray. Good luck with your diagnosis.