Solid pseudopapillary tumors of the pancreas: contrast-enhanced sonographic features.

Objectives: The aims of this study were to determine the features of solid pseudopapillary tumors of the pancreas on contrast-enhanced sonography and correlate them with pathologic findings.

Methods: Five patients with solid pseudopapillary tumors of the pancreas underwent conventional sonographic, color Doppler flow imaging, and contrast-enhanced sonographic examinations. Time-intensity curves were used to calculate the contrast enhancement times, wash-out times, and enhancement patterns of the lesions. Three of the 5 patients also underwent contrast-enhanced computed tomography. All cases were confirmed by surgery and pathologic examination.

Results: The study included 3 women and 2 men. Tumor diameters ranged from 4.4 to 13.0 cm. Sonography revealed round well-defined encapsulated tumors. Two appeared as mixed cystic-solid and 3 as solid masses on conventional sonography. One mass had a macrocalcification. Some areas of blood flow were seen in 3 of the masses on color Doppler flow imaging. On contrast-enhanced sonography, the peripheral rims of the tumors showed isoenhancement during the early arterial phase, and the interiors of the masses showed heterogeneous enhancement consisting of regions of isoenhancement, hypoenhancement, and nonenhancement. Progressive wash-out of the contrast agent during venous phases revealed hypoenhancement compared with normal adjacent pancreatic parenchyma. Pathologic findings showed that each tumor was completely encapsulated and had varying degrees of internal hemorrhage and necrosis.

Conclusions: Solid pseudopapillary tumors of the pancreas have characteristic findings on contrast-enhanced sonography, including peripheral rim isoenhancement and internal heterogeneous enhancement with nonenhanced portions; these features may help differentiate solid pseudopapillary tumors from other pancreatic neoplasms.