Would lung cancer cause enlarged hilar and mediasternal nodes, ggo on chest ct and impaired gas exchange. other lung function tests are normal?

Possibly: There are many different forms of lung cancer however the most common types usually appear as a solitary nodule or mass on CT. GGO can be seen with lymphatic involvement as is suggested by the enlarged lymph nodes described. This can be from infection, cancer or autoimmune diseases such as sarcoidosis and even heart failure. A biopsy of an enlarged lymph node may be required.