Thymic Hyperplasia

I was diagnosed with stage IIIC OC in Oct. 2007. Had complete cytoreduction followed by 8 rounds of carbo/taxol. I am optimistic that I can be a long-term survivor - my CA-125 after surgery was 16, dropped to 7 after 1st chemo, and has been at 6 since compeltion of treatments in April 2008. Had my first post-treatment CT-Scan in August 2008, and my doctor told me that there are some small masses showing that he is pretty sure is scar tissue, and other than that, everything looked fine. I recently had appoitnment with emdical oncologist and at my request, he gave me a copy of the CT Scan report. Other than the scar tissue I was already told about, the report indicates that my cheast area had a trinagular mass of thymic tissue, consistent with thymic hyperplasia. I asked the doctor about this and he said it is very common in children, but very rare in an adult my age ( I'm 50 ), and in any event it was nothing to worry about. I'd like to know what thymic hyperplasia is, what causes it, and is it something to be concerned about ?