¹⁸F-FDG PET/CT imaging features of pancreatic solid pseudopapillary tumor

Objectives Intense FDG uptake in pancreatic solid pseudopapillary tumor was reported, but the reported number of cases is small and few studies focus on the morphologic characteristics of metabolism in lesions. This study aimed to investigate the imaging features and metabolic characteristics of solid pseudopapillary tumor of pancreas (SPTP) using PET/CT.

Methods FDG PET/CT imaging and clinical data of 16 patients pathologically diagnosed with SPT were analyzed retrospectively. The morphology, density and metabolic characteristics of the lesions were observed and analyzed.

Results The lesions were all single tumors mainly with exogenous growth and clear borders. The long diameter of tumor was 1.2-10.4 (4.0±2.7) cm, and shorter diameter was 1.0-7.4 (3.3±2.2) cm. Of which, 4 tumors was demonstrated nearly completely solid (2 lesions showed homogeneous FDG uptake; 1 was inhomogeneous high metabolic lesions with higher metabolic nodules; 1 had FDG uptake similar to normal pancreas). The other 12 demonstrated solid and cystic mixed structures: uneven high metabolic components with higher metabolic mural nodules, mixed with mild metabolic and/or uptake defect. The early SUVmax of all patients was 7. 3±6.8 (2.4～29.1); the early SUVmax of 10 patients with dual-time scans was 6.0±3.4 (2.4～14.1), delayed SUVmax was 6.4±3.2 (2.3～13.4). Paired-Sample t test between early SUVmax and delayed SUVmax of the 10 patients who underwent dual-time scans was performed, the difference was not statistically significant (t=－1.658, P=0.132), R = (7.7±13.6)％. Among the 16 patients, 5 had lesions involving the pancreatic duct or surrounding organs of the pancreas, with early SUVmax of 6.7±4.1 (3.4～13.1). The SUVmax of the remaining 11 patients was 7.5±7.9 (2.4～29.1).

Conclusions Generally, pancreatic solid pseudopapillary tumors were cystic-solid or solid lesions with big volumes, well-defined borders,mostly exogenous growth pattern and calcification. Metabolic characteristic of lesions was that solid parts of the lesion having high FDG uptakes with higher metabolic nodules. Few changes of FGD uptake were seen after delayed scan.

Research Support This study is funded by National Natural Science Foundation of China ((81170435,81471714));China Postdoctoral Science Foundation (20100480545); The International Cooperation projects ofShanghai Science and Technology Committee (10410708800).