What causes lump under the collar bone in case of breast cancer?
I have stage IV metatastic breast cancer that had gone into my lymph nodes, then my lungs. Had a CT/Pet done in Oct and it appeared things were improving. I just discovered another lump on the side of my chest , under the collar bone. I am getting another scan tomorrow. I have been on Gemzar and Novelbine since August. Why would a lump suddenly appear?