Hi there, I had gone through your question and understand your concerns. I see similar cases amongst old age people who visit my clinic. As you have written Male aged 79 years old and having arthritic changes, so it is very common having pain and stiffness in joints in the morning as these are sign and symptoms of osteoarthritis. You are expecting a tumor to which i strictly deny as you are not experiencing any kind of continuous pain, and you have not mention any kind of swelling to the surrounding joint areas. I would suggest you to get X-ray done and of your cervical region because you might be suffering from Cervical degenrative changes which would result in pinching of the cervical nerves and giving you pain in the shoulder region. and X-ray will also rule out the tumor possibility. In the mean time you can start -- heat fomentation at the neck and shoulder region use of proper cushion during night time to rest your head , neck isometric to strengthen your neck muscles. try this for 5-7 days and revert whether your condition is better , worsen or nothing has changed Thanks and regards