Growth on back right shoulder under skin/shoulder blade

I have been diagnosed with a lyphoma several years ago, and know am questioning exactly what this problem is? It is under my right shoulder blade close to the spine and it makes my shoulder swell up and burn to where i cant move around easily until i subside the pain and swelling. It hurts so bad that when it gets rubbed on or pushed on it sends pain down my right upper shoulder and arm and alson feeling it all the way down to my buddix.When this happens i cant raise my right arm above my shoulder blade. It has gotten worse through this past year. What treatment or test do you advise me to pursue  ??