Pancreatic Neuroendocrine Tumors Complicated by Sinistral Portal Hypertension: Insights into Pathogenesis

Abstract

Purpose: To investigate the association between pancreatic neuroendocrine tumors (panNETs) and sinistral portal hypertension (SPH) and provide insights into the pathogenesis. Methods: A retrospective review of panNETs was conducted from our institution for 12 years. Medical imaging findings were analyzed to determine any association with splenic vein thrombosis (SVT) at diagnosis. The cases were further selected based on the criteria for SPH, namely, (1) presence of SVT, (2) gastric varices, (3) patent portal vein, and (4) normal liver function tests. Results: There were 61 patients with panNETs and 8 (8/61) had SVT and gastric varices at diagnosis. Four (4/8) met the strict criteria for SPH while the other four had more conventional portal hypertension. The four with SPH had large tumors located in the tail with splenic vein invasion and three of four presented with bleeding gastric varices. All four patients underwent surgical resection. Mean follow-up was 8.5 years and the hematemesis never recurred. The other four patients (four of eight) with gastric varices had unresectable disease and all died after a mean survival of 29 months. Conclusion: PanNETs appear to be more commonly associated with SVT and SPH compared with other tumors. This could be related to their relatively indolent nature and their intrinsic vascularity. From a surgical viewpoint, the decision to operate depends on many factors including but not limited to the size/stage, grade, and functionality of the tumor and comorbidities. These considerations notwithstanding, the association between panNETs and SPH suggests that there is benefit in timely resection of panNETs located in the tail.

Keywords: gastric varices; pancreatic neuroendocrine tumors; pathogenesis; sinistral portal hypertension; splenic vein thrombosis.

FIG. 1.

(A) Case 1. CT with contrast in the pancreatic parenchymal phase (top row) and portal venous phase (bottom row). A large invasive m arising from the tail of the pancreas extends into the hilum of the spleen. The axial plane images are analogous to the gross pathology (B). The direct invasion of the spleen from the pancreatic tail obstructs the splenic vein to the level of the pc. The sa is encased and remains patent. The splenic vein is obliterated and not visible on either phase. Large gev collateral shunts venous blood from the spleen back into the portal vein through collaterals in the pancreatic head. The dilated and enhancing gev is easily seen on CT running in a tortuous course inferior to the greater curvature of the stomach. (B) Case 1. Cross-section of pancreatic tail where the pancreatic neuroendocrine tumor is invading into the splenic parenchyma. Note the pushing margin of the tumor as bulbous nodules (arrows). Residual normal (lobulated) pancreatic tissue is seen right at the top (arrow). gev, gastroepiploic vein; m, mass; pc, portal confluence; sa, splenic artery.

FIG. 2.

Case 2. This figure shows coronal and axial MR image with fat saturation and contrast in the portal venous phase, and axial T2-weighted images (bottom row). A large invasive m arising from the tail of the pancreas extends into the hilum of the spleen. The direct invasion of the spleen from the pancreatic tail invades and obstructs the splenic vein from the level of the pancreatic tail. The splenic vein is obliterated at the splenic hilum and not visible. A large gev shunts venous blood from the spleen back into the patent portal vein through collaterals in the pancreatic head. The dilated and enhancing gev is easily seen on postcontrast MR images running in a tortuous course inferior to the greater curvature of the stomach. MR, magnetic resonance.

FIG. 3.

(A) Case 2. Photomicrograph showing tumor on right abutting splenic capsule (longitudinal fibrous band) with splenic parenchyma on left (hematoxylin eosin). (B) Case 2. Photomicrograph depicting tumor on right invading into splenic capsule as a broad pushing front with splenic parenchyma on left (hematoxylin eosin).

FIG. 4.

(A) Case 2. Photomicrograph with the tumor having invaded and distending the splenic vein. The lightly eosinophilic areas (arrow) show early thrombus formation (hematoxylin eosin). (B) Case 2. Higher magnification of tumor within splenic vein highlighting the thrombosis (arrow) (hematoxylin eosin).