Imaging features of intraductal pancreatic neuroendocrine tumor / 中华消化外科杂志

ABSTRACT

Objective:To explore the imaging features of intraductal pancreatic neuro-endocrine tumor (PNET).Methods:The retrospective and descriptive study was conducted. The clinicopathological data of 17 patients with intraductal PNET who were admitted to the First Affiliated Hospital of Naval Medical University (Changhai Hospital of Shanghai) from January 2013 to October 2020 were collected. There were 7 males and 10 females, aged (47±13)years. Preoperative contrast-enhanced computed tomography (CT) or magnetic resonance imaging (MRI) of the pancreas was performed on patients. Observation indicators (1) imaging features of intraductal PNET, including ① imaging features of CT and ② imaging features of MRI; (2) treatment and histopathological examination of intraductal PNET. Measurement data with normal distribution were described as Mean± SD and count data were described as absolute numbers. Results:(1) Imaging features of intraductal PNET. ① Imaging features of CT 17 patients underwent preoperative contrast-enhanced CT of pancreas. There were 9 cases with tumor located in the head of the pancreas, 5 cases with tumor located in the neck of the pancreas and 3 cases with tumor located in the body and tail of the pancreas. The tumor diameter of the 17 patients was (8.7±2.5)mm, with a range of 5.2?15.5 mm. The tumor shape was round-like in the 17 patients. All the 17 patients showed isodensity on plain CT and markedly enhancement in arterial, venous and portal phases on enhanced CT. The degree of enhancement of tumor was higher than surrounding normal pancreatic parenchyma. All tumors of 17 patients were located at the truncation of main pancreatic duct (MPD) dilation, showing abrupt change in caliber of MPD without the "beak sign". The diameter of dilated MPD was (11.4±5.3)mm, with a range of 4.5?22.5 mm. Other imaging manifestations of the 17 patients included 11 cases with pancreatic parenchymal atrophy, 1 case with retention cyst, 1 case with choledochal dilation, 1 case with calcification, and all cases without cystic degeneration or hemorrhage. ② Imaging features of MRI preoperative contrast-enhanced MRI was performed in 14 patients. Five cases showed slightly low signal but 9 cases showed unclear on T1-weighted imaging. Five cases showed low signal, 2 cases showed slightly high signal but 7 cases showed unclear on T2-weighted imaging. Of the 14 patients, 9 cases showed diffusion limited on diffusion weighted imaging and 5 cases showed unlimited diffusion. Nine cases showed marked enhancement in tumor higher than in normal pancreatic parenchyma, but 5 cases were unclear on contrast-enhanced MRI. (2) Treatment and histopathological exmination of intraductal PNET all the 17 patients underwent surgical treatment, including 9 cases with pancreaticoduodenectomy, 4 cases with distal pancreatectomy and splenectomy, 4 cases with pancreatic segmentectomy. Postoperative histopatho-logical examination results showed 10 cases of G1 and 7 cases of G2, including 1 case of G2 with lymph node metastasis, 1 case of G2 with lymph node and liver metastasis. The pathological gross showed that the tumor body was mainly located in the pancreatic duct and blocked the pancreatic duct, with upstream pancreatic dilation. There were pancreatic acinar atrophy and fibrous tissue hyperplasia. The tumor was grayish-yellow or brownish red, solid, medium in texture and well-defined with the surrounding tissues. Microscopically, the tumor of 17 patients was mainly located in the pancreaic duct and invaded into surrounding pancreatic parenchyma. The cells of tumor were polygonal with a central nucleus, but the mitosis was rare. The cytoplasm was eosinophilic or hyaline. The tumor stroma was mainly collagen fiber with abundant capillary network.Conclusions:The imaging features of intraductal PNET are small size, marked enhancement on contrast-enhanced CT and MRI. The tumor obstructs the MPD with distal MPD dilation and pancreatic parenchyma atrophy.