Utility of EUS in Diagnosing a Retroperitoneal Lymphangioma Masquerading as a Pancreatic Cyst

Abstract

Purpose: A 56 year old male veteran was referred to the gastroenterology clinic for evaluation of an incidental retroperitoneal mass on MRI performed for evaluation of back pain. The mass was described as cystic, 6 cm in cephalocaudal dimensions, anterior to the inferior vena cava at the level of renal veins. This mass was not present on a previous MRI scan performed three years ago. The veteran did not complain of abdominal pain, nausea, emesis, jaundice, weight loss or anorexia. No prior history of acute or chronic pancreatitis could be elicited. Physical exam was unremarkable. Basic laboratory tests revealed normal complete blood count, basic metabolic panel, liver function tests and serum lipase. A follow-up CT scan showed a cystic mass near the uncinate process of the pancreas, duodenum, right kidney and the inferior vena cava. Endoscopic ultrasonohraphy (EUS) showed a 6 cm nonseptated cyst posterior to the uncinate process of the pancreas. FNA of this cyst was performed under EUS guidance and yielded 8 ml of milky fluid. Amylase content of the fluid was 51 U/L. Carcinoembryonic antigen (CEA) level in the fluid was reported to be 1.0 ng/ml. Triglyceride level in the cystic fluid was extremely elevated at 2100 mg/dl. Having excluded pancreatic pseudocyst, serous and mucinous neoplasms of the pancreas, a diagnosis of retroperitoneal lymphangioma (chylous cyst) was made. The patient was reassured given the benign nature of the cyst. Since the patient was asymptomatic, surgical excision was not required. Lymphangiomas are rare cystic tumors of the lymphatic system. Retroperitoneal lymphangiomas constitute 1% of all lymphangiomas. Their development is believed to be due to an abnormal connection between the iliac and retroperitoneal lymphatic sacs and the venous system, leading to lymphatic fluid stasis in the sacs. They are mostly asymptomatic but may present with abdominal pain, nausea, vomiting and anorexia as size increases. Pre-operative diagnosis is challenging and is usually a diagnostic dilemma. The final diagnosis of lymphangioma is usually based on pathological examination of the surgical specimen. Prognosis is excellent since they are almost always benign. Through this report, we have highlighted the role of EUS-FNA in the diagnosis of this rare entity and prevented the surgical excision of this benign lesion.