Duodenal mass in a patient with rheumatoid arthritis

A 41-year-old woman who had been followed for rheumatoid arthritis (RA) was admitted to the gastroenterology clinic with a complaint of dyspepsia and bloating for a month. Her past-medical history was insignificant other than RA and she was using infliximab for last two years. The physical examination was unremarkable. Laboratory tests such as complete blood count, creatinine, liver enzymes were within normal range and the C-reactive protein level was 9.1 mg/L (N: 0–6). Endoscopy of upper gastrointestinal tract showed erosive gastritis and a mass partially obstructing the lumen at the distal site of the second part of the duodenum (Figure 1A-1B). There were ileal ulcerations at colonoscopy. Multiple biopsies were taken from the duodenum, stomach and ileum. Thoracoabdominal computed tomography (CT) scan revealed a mass lesion at 3rd part of duodenum and uncinate process level of pancreas (Figure 1C), multiple enlarged lymph nodes in the intraperitoneal and retroperitoneal area, and multiple nodular lesions, less than 5 mm in diameter, in both lungs. What could the patient’s diagnosis be?