I have plasmacytoma and recently discovered another tumor in my neck, please advise?

A few months ago I was diagnosed with plasmacytoma in my tonsil after the tonsil was removed. I underwent all the skeletal testing to check for multiple myloma and all was negative. During the MRI another plamacytoma tumor was found in the muscle in my neck and shortly after that my throat was scoped and another plasmacytoma tumor was found in my larynx. My doctors are telling me this is very rare. Could I have your thoughts on this. Thanks