Nonfunctioning cystic neuroendocrine tumor of pancreas. Presentation of an unusual case.

Pancreatic endocrine neoplasms are a group of tumors that sporadically affect this gland, although their etiopathogenesis, diagnosis and treatment are still object of debate. The approximate incidence of these neoplasms is from 1 to 2% of all pancreatic tumors and their clinical symptoms depend on the production of hormones or biologically active amines. The cystic presentation of these tumors is a much rarer situation (approximately 4.5%), which usually makes their preoperative diagnosis difficult. Therefore, they are frequently confused with other cystic neoplasms of the pancreas with different therapeutic approaches, such as serous cystadenomas, mucinous cystic neoplasms, intraductal papillary mucinous neoplasms, and epithelial cysts, among others. The aim of this letter is to present 3 new cases of nonfunctioning pancreatic neuroendocrine tumors with predominantly cystic characteristics. The patients are two females, aged 53 and 63, and one male, aged 25. The first two patients presented no specific symptoms. The male patient was in follow-up for a diagnosis of multiple endocrine neoplasia type 1 (MEN-1) and Cushing’s disease. The diagnosis of the pancreatic lesions was incidental. Computed tomography showed evidence of a cystic formation with hypodense areas measuring 3.5 cm in the body of the pancreas in the first case (Fig. 1A). In the second case, a solid cystic lesion was detected in the uncinate process measuring 1.7 cm (Fig. 2A), which was confirmed by endoscopic ultrasound. And, in the third case, magnetic resonance showed a predominantly cystic lesion with cell thickening in the tail of the pancreas measuring 6.2 cm. Surgery was indicated in all cases: in the first, pancreatectomy of the body and tail of the pancreas with splenectomy (Fig. 1B); in the second, pylorus-preserving pancreaticoduodenectomy (Fig. 2B); and, laparoscopic distal splenopancreatectomy in the third case. This last patient presented a type Ipancreatic fistula in the postoperative period. Hematoxylin-eosin confirmed the diagnosis of well-differentiated pancreatic endocrine neoplasm, with mitotic index inferior to 10 fields in the 3 cases. Immunohistochemistry showed positivity for chromogranin A, cytoplasmic neuroendocrine marker and neuron-specific enolase in the first case. The second case was positive for chromogranin A, synaptophysin, progesterone receptor 1A6, Mib-1, AE1, AE3 and the proliferation rate (Ki-67) was 5%. In the third patient, this method was positive for somatostatin, enolase monoclonal, chromogranin A, synaptophysin and glucagon, with Ki-67 less than 1%. The first 2 patients had no symptoms in follow-up, and the third patient continues in clinical and endocrinological follow-up. The development of diagnostic imaging methods in recent decades has undoubtedly resulted in the diagnosis of a series of asymptomatic pancreatic neoplasms, which before would probably have gone undetected with traditional methods. This has also led to controversial situations in the diagnosis and especially the treatment of certain diseases. Among these incidental diagnoses, pancreatic endocrine neoplasms are the most frequent. Their low incidence causes great diagnostic difficulties due to the absence of characteristic disease symptoms. This diagnostic difficulty can increase when these endocrine tumors adopt a cystic form,