I have had this lump on my upper arm, underneath about three inches from my armpit, for almost four years. I have gone to the doctor and had her look at it. All she said was it was probably nothing. It gives of a throbbing pain every so often and is tender to the touch. I am worried that it might be a tumor because I have recently had my thryoid removed because of two tumors. Should I have this evaluated again and ask if it is a tumor.