I Am A 47 Yr Old Woman With Vasculitis.microscopic Polyangiitis

I am a 47 yr old woman with vasculitis.microscopic polyangiitis with glomerulonephritis from about 9 years ago.at presentation of my illness P-ANCA was positive but it became negative with treatment during 2 month.i was on MMF and prednisone.2 months ago P-ANCA was positive again and I had kidney biopsy again.
the major finding in biopsy was active `focal`anca associated glomerulonephritis.my doctor changed MMF to AZATHIOPRINE 150 mg and increased dose of prednisone to 60 mg.i am worried about side effects of AZATHIOPRINE.specialy lymphoma.i want know about the risk of lymphoma with AZATHIOPRINE and prognosis of my illness.cr is 0.7 mg/ds