Retroperitoneal inflammatory pseudotumor presenting as a pancreatic mass.

Context: The inflammatory pseudotumor is a rare chronic inflammatory disease not considered as a real tumor but with a similar locally aggressive behavior. Although usually located in the lungs it may be found in other organs.

Case Report: We present the clinical case of a 66-year-old woman diagnosed with inflammatory pseudotumor after undergoing an exploratory laparotomy due to a large non resectable abdominal mass. Preoperative abdominal CT revealed a large solid polylobulated mass involving the pancreas, duodenum, hepatic hilum and superior mesenteric artery. Percutaneous fine needle aspiration and tru-cut biopsies ruled out lymphoma but did not achieve a definitive diagnosis. CD68 antibody positivity of the surgical biopsy specimen confirmed the histiocytary origin. Ki67 antibody expression was 10%. The final diagnosis was inflammatory pseudotumor rather than malignant fibrohistiocytoma based on the features and the severity of the inflammatory component. Chemotherapy was ineffective and the patient died 25 months later because of local progression and infection of the tumoral necrotic tissue.

Conclusion: Although inflammatory pseudotumor is not considered to be a real tumor, its aggressive local growth is similar to that of malignant soft tissue sarcomas. The only curative option is the complete surgical resection, albeit frequent recurrence.