My mom was diagnosed with pneumonia and a mass on lungs..is it possible for a lung cancer?

Yes: This is a common way for lung cancer to present. A biopsy will tell for sure. I am glad you are there for your mother at this challenging time.

Yes, may be : Lung cancer commonly presents as an infiltrate on a chest x-ray initially diagnosed as pneumonia when the problem may be a cancer blocking that part of the lung and causing the x-ray changes. Any infiltrate on a chest x-ray that doesn't clear up on antibiotics should have a ct scan of the chest to look for a cancerous mass. A pet scan can add further diagnostic accuracy but a biopsy is needed.