What Causes Protruded Mass Beneath The Ribcage Post Removal Of Upper Left Lobe?

I had Lung Cancer and had my upper left lobe removed. Since than which was six years ago, I've had a hard mass fall from underneath my rib cage when I am in certain positions. It's the size of the inside of my small
hand. The only way the mass will go back in place is for me to lay flat on the floor with my arms raised above my head for 30 seconds to a minute for it to go back in place. I can hear the sound of it moving. I've had numerous CT scans and they can't tell me what it is because I am lying flat on my back and it's in place. I have
been from Dr. to Dr. and have been told it could be a hernia, muscle skelton, or a muscle that's know longer
functioning. In additon I have a degenerative disc disease. I've had four back operations, and two fusions
one the upper and the other of the lower back. Now I have another disc dislocated disc and stenosis has developed over the years that has become so painful. I don't know what to do anymore. I've become so
discouraged with the pain and depression. Please help...Thank You