Pancreatic Lymphoepithelial Cyst: A Rare and Benign Entity Still Frequently Treated with Unnecessary Surgery

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Purpose: This is the case of a 75 year-old male patient who presented after the incidental finding of a 90 mm cyst adjacent to the tail of the pancreas, which was found during a computed tomography (CT) angiogram ordered for evaluation of abdominal aortic aneurysm grafting. The patient had no history of acute or chronic pancreatitis, nor any history of alcohol abuse, or significant abdominal trauma. The initial differential diagnosis included cystic neoplasm and pseudocyst. A magnetic resonance cholangiopancreatography (MRCP) was performed and revealed a 90 mm cyst with a solid component adjacent to the tail of the pancreas. The patient was referred for endoscopic ultrasound and fine needle aspiration (EUS-FNA) which revealed a hypoechoic, heterogeneous, pancreatic cystic mass in the region of the tail of the pancreas, measuring 95.3 mm x 53.7 mm. The border was poorly demarcated and was abutting the spleen. The microscopic examination of the FNA sample revealed necrotic debris with rare clusters of columnar epithelial cells, with no evidence of malignancy. However, no definitive diagnosis could be made. The Patient was referred to surgery and distal pancreatectomy with splenectomy was performed. Pathology revealed a cystic lesion, which was lined by keratinizing squamous epithelium overlaying lymphoid tissue made up of small to medium sized lymphocytes with germinal center formation, consistent with a lymphoepithelial cyst. The postoperative period was complicated by the development of a paripancreatic abscess, which was treated by percutaneous drainage and antibiotics. The recovery was then uneventful. This case demonstrates that while it may be true that the majority of cystic lesions in and around the pancreas are pseudocysts or cystic neoplasms, there are a number of rare and benign conditions that present in similar fashion, including pancreatic lymphoepithelial cysts. Despite the increasing availability of high quality CT scans and MRIs, as well as the evolution of endoscopic ultrasound, which make the diagnosis of pancreatic cystic masses more readily prior to surgeries, the diagnosis of lymphoepithelial cysts still represents a true challenge due to a spectrum of nonspecific imaging and serological findings, making its differentiation from cystic neoplasms difficult. Hence surgery is still considered, in certain circumstances, for definitive diagnosis.