For about two weeks, I have had pain in the underside (back) of my right arm. It has increased in severity and now seems to originate at a spot in my trapezius muscle. The entire muscle does not hurt, just one small area. The pain is beginning to radiate into my shoulder and neck a bit, but the pain is very uncomfortable. It does not feel like musculoskeletal pain I have experienced in the past. I had a lumpectomy for stage 2 breast cancer in my left breast in May 2013, TC chemo X4 (June 2013-August 2013) and 33 radiation treatments completed in November 2013. I m not certain the BC is relevant, but I am covering all the bases that may help in a possible diagnosis. I am in a 90 day waiting period for insurance coverage, and can t seek expensive diagnostic tests at this time. Thank you for any assistance you can offer.