Sue, I was told the determination was made by viewing the MRI with contrast. I looked it up on the web, and doctors determine how the tissue appears under contrast.

Though, someone on this site was told their tissue was benign but after the biopsy, it was deemed malignant.

So, I'm not really confident, but I have read that most of the tissue on a thymus is benign. Once I obtain some insurance, I will schedule an appointment with the same doctor, because I need him to order the next round of MRIs.

After that, I will most likely request another specialist.