Pancreatic Retroperitoneal Fibrosis Masquerading as a Pancreatic Mass: A Diagnostic Quandary

Abstract

Retroperitoneal fibrosis (RPF) is a cryptic condition affecting 0.1 per 100,000 patients per year. The pathophysiologic etiology is believed to be autoimmune in nature, resulting in fibrotic tissue deposition within multiple organs. This case highlights an unusual primary pancreatic manifestation of an already exceedingly rare disease. The patient is a 45 year-old male with no significant past medical history who presented with painless jaundice. Computerized tomography revealed a 3 cm pancreatic-head mass encasing the vasculature and ductal system. An endoscopic ultrasound with fine-needle-biopsies (EUS-FNB) of the mass and endoscopic retrograde cholangiopancreatography (ERCP) were performed. The EUS characterized the lesion as a 34 x 28 mm ill-defined heterogeneous mass with multiple collateral blood vessel in the pancreas, suggestive of underlying portal hypertension, correlating with an endoscopic finding of esophageal varices. On ERCP, the common bile duct was dilated to 14mm with a shelf-like distal stricture, treated with a 10 French, 5cm plastic biliary stent. Initial fine needle biopsy results, while inconclusive, could not rule out malignancy or autoimmune pancreatitis. Repeat EUS-FNB with 7 needle passes again returned with non-malignant findings. He subsequently underwent laparoscopic biopsy of the pancreatic mass which revealed sclerosing collagenous fibrosis, displaying lymphoplasmacytic inflammation, suggestive of RPF. Infectious and malignant etiologies for RPF were excluded. He was started on steroids with symptomatic improvement and mass stabilization on subsequent imaging. Through extensive review of the literature, RPF encasing the pancreas without ureteral or periaortic involvement has scarcely been documented. In this case, the mass effect of the fibrosis resulted in biliary obstruction and pre-sinusoidal portal hypertension, and highlights the difficulty in diagnosing an exceedingly rare condition masquerading as pancreatic malignancy. This patient had a protracted course involving multiple sub-specialties, numerous endoscopic procedures, and ultimately a diagnostic surgery. The seemingly elusive diagnosis of RPF conclusively requires histologic certainty prior to treatment. When finally diagnosed, steroids are the mainstay of therapy for RPF.1424_A.tif Figure 1: Dense fibrosis with keloid-type collagen fibers1424_B.tif Figure 2: PET scan showing avid FDG uptake at pancreatic lesion1424_C.tif Figure 3: No Caption available.