Thanks Abby. It isn't my thyroid, according to my docs. The thyroid is higher on the throat than this growth. This one is nestled right between the ends of the left and right collarbones. I understand that they can occur from RA which is probably the culprit but thought I'd check to see if it could be from the thymus since I have MG symptoms.

I mis-wrote "spreading" as today I realized that the growth is not connected to the swelling around the collarbones.
all the best