Differentiation between benign and malignant solid pseudopapillary tumor of the pancreas by MDCT

Purpose: The purpose of this study was to determine if characteristic features on computed tomographic and (or) magnetic resonance imaging can differentiate benign and malignant solid pseudopapillary neoplasms (SPN).

Materials and methods: A total of 82 pathologically diagnosed SPN patients were included. CT and MRI were reviewed by 3 radiologists. Each tumor was analyzed through the clinical and imaging features.

Results: The highest occurrence of malignant SPN was observed in the group of patients (11-19 years old) followed by the group of patients (50-65 years old). When the tumor was located in the tail and the size was equal or larger than 6.0 cm, the positive and predictive value, the predictive value, sensitivity and specificity for a malignant SPN were 61.5%, 100%, 100% and 78.6%, respectively. Presence of complete encapsulation was more frequent in benign SPNs, but focal discontinuity in the malignant SPNs. Amorphous or scattered calcifications, all near-solid tumors and presence of upstream pancreatic ductal was found in the benign SPNs.

Conclusion: A focal discontinuity of the capsule, large tumor size (>6.0 cm) and a pancreatic tail location may suggest malignancy of SPN. In contrast, tumors with amorphous or scattered calcifications, and all near-solid tumors may be indicative of benignancy. Age (less than 20 or more than 50 years old) is a possible risk factor of SPN. In comparison to other pancreatic neoplasms, such as ductal adenocarcinoma, a complete/incomplete pseudo-capsule, without upstream pancreatic duct dilatation and lymph nodes metastasis, and the presence of internal calcification and hemorrhage are more likely SPN.