Hi Debbie
My dad has adenocarcinoma of the lung. The biggest tumor he has in the upper (apex) of his right lung. He too has had alot of shoulder pain. His doctor said that tumor (previously 3.cm x 2.2 cm) is probably laying on a nerve and causing pressure. Since he's been on chem o the pain has subsided and the scans also show that his tumor is shrinking. He is stage IV and inoperable because it is in both lungs and in his lymph nodes. He also takes zofran and compazine for the nausea. Right now all he's needed for the pain was just some ibuprofin . Good luck with your mom and I hope all is well.
Tracey