Endoscopic Ultrasound-Guided, Needle-based Confocal Laser Endomicroscopy in the Diagnosis of Cystic Pancreatic Neuroendocrine Tumor: Emerging Imaging Criteria From Surgical Pathologic Correlation in Two Cases

Abstract

Introduction: Cystic pancreatic neuroendocrine tumors (NETs) are relatively rare, with the reported incidence of < 10% of resected pancreatic cystic lesions. Preoperative diagnosis of cystic pancreatic NET remains challenging. Needle-based confocal laser endomicroscopy (nCLE) during EUS guided fine needle aspiration (EUS-FNA) has been shown to be useful in other pancreatic cystic neoplasms (ex Intraductal papillary mucinous neoplasia or IPMN). However, the utility of EUS-guided nCLE in the diagnosis of cystic pancreatic NET has not been reported, and imaging criteria based on surgical pathologic correlation has not been established. Methods: Under EUS guidance, the pancreatic cystic lesion was punctured with a 19-gauge FNA needle. After confirmation of cyst entry, fluorescein was injected intravenously. The nCLE probe was then advanced through the needle into the cyst, and the cyst wall was carefully imaged. Results: [Case 1] A 65 year-old-male presented for rapid enlargement over one year of a known pancreatic cystic neoplasm. On EUS, a 23X22 mm unilocular cystic lesion was seen in the pancreatic tail. There was no evidence of wall thickening or mural nodules. nCLE demonstrated a high density of dark thick cord-like structures or dark nest-like structures (Fig 1 ). There was no evidence of papillary projections, dark rings, or a superficial vasculature network, suggesting IPMN or serous cystadenoma, respectively. Laparoscopic distal pancreatectomy was performed. Histology of the resected specimen revealed well-differentiated pancreatic NET. nCLE images corresponded well to histological images (Fig 2).Figure 1Figure 2[Case2] A 71-year-old male with diabetes presented for evaluation of a pancreatic tail lesion seen on CT during investigation of abdominal pain. EUS demonstrated a 21X16 mm unilocular cystic lesion in the pancreatic tail with partial wall thickening. On nCLE, a high density of dark cord-like structures was observed. Distal pancreatectomy was performed and histology revealed a pancreatic NET. Conclusion: EUS-guided nCLE images correlated well with surgical pathology in 2 cases of cystic pancreatic NET. A high density of dark thick cord-like structures or dark nest-like structures may be important diagnostic criteria. If these criteria are prospectively validated, nCLE may play a role in the diagnosis of cystic pancreatic neuroendocrine tumors.