So far, pancreatic serous cystadenoma coexistent with neuroendocrine tumor is still a rare pancreatic disease. To date, cases were reported sporadically(2–5). Our case presented here is a 67-year old man. Although the ethnic origin is still unverified, it seems women have a higher incidence according to the literature(3, 6). In the case presented, the pancreatic double tumors were not discovered until the operation. There was only one mass detected preoperatively by different examinations with different results. What interesting is CT and EUS indicated that the pancreatic tumor was IPMN, while MRI was serous cystadenoma. Moreover, EUS biopsy considered highly differentiated neuroendocrine tumors. To our best knowledge, asymptomatic pancreatic cystic neoplasms with a size of less than 3 cm is recommended employing a conservative approach(7). According to the European Neuroendocrine Tumor Society, surgical resection is recommended for PNET > 2 cm(8). However, the patient had been enduring abdominal pain for a long time and he was firmly requested for operation. Besides, surgery is still the treatment of choice due to the significant malignant potential(9). Sharpe et al evaluated 380 PNETs in the National Cancer Data Base (NCDB). Five-year overall survival was 82.2% in the operation group and 34.3% in the observation group. They concluded that surgical resection provided an overall survival benefit for patients with small pancreatic neuroendocrine tumors(10). Finally, a distal pancreatectomy was performed. The postoperative histopathology discovered the real PNET incidentally which was not the lesion examined preoperatively. Similarly to the present case, Alasio et al reported a 78-year-old female case whose neuroendocrine tumor was discovered incidentally after complete resection of the serous cystadenoma(5). Consequently, the coexistence of two pancreatic tumors is easily misdiagnosed, so comprehensive evaluation is necessary before surgery.
The association between PNET and SCA remains unknown. One hypothesis is in light of the biphasic differentiation of the pancreatic ductal stem cells. Indeed, the biphasic differentiation from pancreatic ductal stem cells to either glandular epithelial or neuroendocrine cell has been found in many pancreatic tumors(11). While some tumors combine the epithelial and neuroendocrine features within the same cells, others show the epithelial and neuroendocrine cells developing concurrently within the same tumor(4). Further researches are still needed to figure out the association of coexistent PNET and SCA.
Enhanced CT and MRI are commonly used during the diagnosis of pancreatic diseases. Using these image examinations, the tumor size and location can be easily verified as well as the anatomical relationship with surrounding organizations(12). EUS can effectively avoid the interference of intestinal gas, bone, and subcutaneous fat. Combined with high-frequency probe, a high-definition image is formed and the biopsy puncturing distance shortens. Furthermore, the immunohistochemical technique contributes to differential diagnosis on the molecular level. Kim Y. W used immunohistochemical studies dealing with PNET admixed with SCA firstly in the literature report(1). Neuron-specific enolase (NSE) and chromogranin A (CgA) are always positive in PNET. In the present study, we regret that somatostatin-receptor imaging, which contributed to exclude distant metastasis, was missed due to lack of necessary device.
To summarize, SCA coexistent with PNET is rarely found during clinical practice. The component of PNET may not be confirmed until operation. Based on the recorded cases, the malignant potential, clinical characteristics, treatment, and prognosis remain further researches.