An 85-year-old woman with rheumatoid arthritis that was treated with azathioprine presented with a posterior thoracic soft-tissue mass. A computed tomographic scan demonstrated a large mass in the chest wall that extended into the pleural space and several pulmonary nodules that were consistent with metastatic disease. A fine-needle biopsy was performed, and a morphologic diagnosis of sarcoma was made. As the patient was relatively asymptomatic and the lesion was inaccessible to a surgical procedure, no therapy was recommended. Therapy with azathioprine was discontinued. One year later, the mass had resolved. To our knowledge, this is the first reported case of a soft-tissue sarcoma complicating azathioprine treatment of rheumatoid arthritis.
Arch Intern Med. 1996;156:1573-1576