Robotic distal pancreaticosplenectomy for large complex oncocytic pancreatic neuroendocrine tumors: a rare pancreatic neoplastic variant

Abstract

Background: Minimally invasive techniques are being used increasingly in patients with pancreatic neuroendocrine tumors. Oncocytic pancreatic neuroendocrine tumors are rare morphologic variants often diagnosed after surgery due to the lack of specific clinical features in preoperative fine-needle aspiration. Unlike other subtypes, oncocytic pancreatic neuroendocrine tumors may exhibit more malignant behavior. We report a rare case of a patient with a large, complex oncocytic pancreatic neuroendocrine tumor who underwent curative-intent robotic left pancreaticosplenectomy. We demonstrate the benefit of the robotic platform in facilitating dissection of large pancreatic tumors. Methods: This is a 57-year-old female with hypertension, diabetes, hyperlipidemia, and morbid obesity presenting with a large symptomatic mass in the tail of the pancreas. Contrast-enhanced computed tomography (CT) identified a 5.6 x 5.5 x 4 cm complex solid-cystic tumor in the tail of the pancreas. She underwent robot-assisted laparoscopic left pancreatectomy. The splenic artery was dissected first with an EndoGIA stapler. Intraoperative ultrasound confirmed the location of the pancreatic tumor. Once mobilized away from surrounding structures, the pancreas was divided with an EndoGIA stapler over two minutes, with progressive pressure to compress the gland. The splenic vein was divided, with great care taken to identify and protect the inferior mesenteric vein. The tumor was dissected off the retroperitoneum and the specimen was sent to pathology. Results: Blood loss was negligible. There were no perioperative complications. Final surgical pathology revealed a grade 1 oncocytic pancreatic neuroendocrine tumor with no nodal involvement and negative surgical margins. Ki67 was 2.8% and mitotic count was 2 per 50 high power fields. The tumor exhibits cystic areas, fibrous bands, and partial encapsulation with invasion into the fibrous capsule and focal extension into peripancreatic fat. She recovered well after surgery without any complications. Conclusion: Contrary to other morphologic variants, oncocytic pancreatic neuroendocrine tumors have been found to have more aggressive malignant behavior. Minimally invasive pancreatectomy may lead to minimal blood loss and allows for adequate margin clearance of large, complex pancreatic tumors in the body and tail of the pancreas. The robotic approach adds precision to the movement while adhering to oncologic principles, which can be helpful when treating morbidly obese patients with large pancreatic tumors.