A Shrinking Pancreatic Neuroendocrine Tumor Demonstrated Over 34 Months of Surveillance by Endoscopic Ultrasound

Abstract

Introduction: The patient is a 65-year-old man with morbid obesity (BMI 46.3 kg/m3) and hypertension who presented to the ER with acute onset abdominal pain and vomiting. He was managed for gastroenteritis and improved overnight, but a CT scan obtained by the ER showed an incidental 1.5-cm hyperdense mass in the pancreatic uncinate process. The patient reported no recent weight loss, oily stools, chronic abdominal pain, or jaundice. Liver function studies, pancreatic enzymes, and CA 19-9 were all normal. He underwent endoscopic ultrasound (EUS) of the lesion, which revealed a 1.7-cm diameter hypoechoic, round, regular-appearing, homogenous lesion in the uncinate process. Eventual fine needle aspiration revealed atypical cells positive for synaptophysin and chromogranin with nuclear staining for Ki67 <2%, consistent with a low-grade well-differentiated neuroendocrine tumor (NET). An octreotide scan was unremarkable as were hormone studies for a functioning NET. Due to the low-grade nature of the tumor, the lack of patient symptoms, and the patient’s comorbid conditions, he elected not to have surgery, but rather, for continued surveillance of his lesion. Over a 34-month period, the patient was surveyed with EUS and his tumor was noted to serially shrink from 1.7 cm in diameter at the time of diagnosis to 0.8 cm in diameter at last follow-up. Pancreatic neuroendocrine tumors are rare lesions and make up 3% of all primary pancreatic neoplasms. A recent rise in the incidence of these lesions may be secondary to the increased sensitivity of routine transabdominal imaging studies for detecting incidental, asymptomatic tumors (as was the case here). They can be both functional and nonfunctional depending on the presence of hormone secretion (insulin and gastrin being the most common). While larger (>2 cm) nonfunctional low-grade lesions should be removed, small lesions can be followed if the patient’s operative risk is felt to be high, as natural history studies have shown tumor stability and benign behavior in many of these lesions. This case of a pancreatic neuroendocrine tumor, not only remaining stable in size, but actually shrinking by over 50% in diameter over a 34-month period further illustrates the role of surveillance for low-grade, well-differentiated pancreatic NETs in patients with high operative risk.