Rare Presentation of Cystic Nonfunctioning Pancreatic Neuroendocrine Tumor: A Case-Series

Abstract

Purpose: Pancreatic cysts are often identified incidentally on body imaging. Cysts >3 cm are often evaluated by endoscopic ultrasound (EUS), and those <1 cm followed by serial imaging. We present two cases in which EUS of pancreatic cysts <1.5 cm in size revealed nonfunctioning pancreatic neuroendocrine tumors (PNET). A 36-year-old man presented with an exacerbation of chronic epigastric pain. He also reported subjective fevers, skin flushing and pruritus. Computed tomography (CT) of the abdomen and pelvis showed a subcentimeter hypodensity in the body of pancreas. EUS showed a thick walled, anechoic, single compartment cyst in the pancreatic body measuring 10 x 7 mm. Fine needle aspiration (FNA) was consistent with a well-differentiated neuroendocrine tumor. Nuclear octreotide scan and hormonal studies were normal and the tumor was determined to be localized and nonfunctioning. A 59-year-old man presented with two weeks of right flank pain. CT scan revealed a 1.5 cm exophytic cystic area in the tail of the pancreas contiguous with the posterior wall of the stomach. EUS showed a 15 x 15 mm anechoic, multicystic, distally enhancing lesion with peripheral mural nodularity in the pancreatic tail. FNA revealed neoplasm and the patient underwent distal pancreatectomy and splenectomy. Surgical resection specimen pathology showed a low-grade PNET with negative margins. Lymph nodes sampled were negative for malignancy and this was determined to be a nonfunctioning neuroendocrine tumor. Pancreatic cysts are increasingly discovered as abdominal imaging studies have improved in sensitivity and are more frequently performed. EUS with FNA has emerged as the modality of choice for obtaining tissue and fluid from these lesions. The majority are pseudocysts while a growing minority represent pancreatic cystic neoplasms. PNETs are rare and comprise less than 5% of pancreatic malignancies. They are commonly divided into functioning (hormone-producing) and nonfunctioning tumors. In 2006, a pancreatic neuroendocrine tumor presenting with vision changes due to demyelinization of the optic nerve was reported. In 1998, Koutalas et al. reported an 18 cm nonfunctioning PNET. In 1994, Schwartz et al. reported 3 cases of large nonfunctioning PNET presenting with symptoms due to mass effect. There are no previously reported cases of a small cystic nonfunctioning PNET. Although diagnosis of cystic pancreatic neuroendocrine tumors is rare, our experience shows that endosonographic evaluation of incidentally found small (<3 cm) pancreatic cysts should be considered. Once diagnosed, an assessment for hormone production should be conducted as well as referral for consideration of surgical resection.