I have a neck mass that above my left collar bone that changes size.  Yesterday, it was almost gone, now it is back.  I have had blood work and a CT scan.   Lymphonia, lung disease, thyroid disease have been initally ruled out.   The CT scan showed soft tissue swelling.    What could be the cause/
Hello, It sounds like you may have some sort of cyst. These are usually not a serious problem. Cancer and lymph nodes do not swell up and go down like this. Regards