What Causes Right Chest, Sternoclavicular Joint, Sternum, Shoulder And Arm Pain?

Hello, I was hoping if this place could help. My girlfriend has been suffering from pain in the past 6-7 months, and all of the physicians we have visited can't seem to pinpoint what's wrong with her. I'm terrified that it's something life threatening, and I'm frustrated that we're not getting any answers. She is 36, and used to be a light smoker for 4 years but quit several months ago. Her symptoms include: 1.) Right chest pain, upper region. 2.) Sternoclavicular joint pain. 3.) Pain on sternum and rib bone junction on the right side; dull aching pain 4.) Back of shoulder pain, below the scapular. 5.) On and off pain on the right upper arm area. 6.) Posterior lymph node swelling on right neck; dull pain that seems to have been getting worse with time. Our physicians have ruled out lung cancer, X-Rays and CT's are clean, and MRI's showed a slight pleural thickening. Multiple blood tests all came back clean. We are still in the middle of running more tests, but so far, none are conclusive; treatment hasn't helped much, since we can't isolate what the specific underlying problem is. We've been told that it could either be lupus or rheumatoid arthritis, but upon more consults, she's not showing any of the major symptoms that are tied to those conditions...... We are still worried it's possibly cancer......we are praying it's not. Thanks for any help that we can receive....