Imaging differentiation of solid pseudopapillary neoplasms and neuroendocrine neoplasms of the pancreas

Purpose: The present study aimed to compare the computed tomography (CT) and magnetic resonance imaging (MRI) features of solid pseudopapillary neoplasms (SPNs) and pancreatic neuroendocrine neoplasms (pNENs). Method: Lesion imaging features of 39 patients with SPNs and 127 patients with pNENs were retrospectively extracted from 104 CT and 91 MRI scans. Results: Compared to pNEN patients, SPN patients were significantly younger (mean age 51.8 yrs versus 32.7 yrs) and more often female (female: male ratio, 5.50:1 versus 1.19:1). Most SPNs and pNENs presented as welldefined lesions with an expansive growth pattern. SPNs more often appeared as round or ovoid lesions, compared to pNENs which showed a lobulated or irregular shape in more than half of cases (p <0.01). A surrounding capsule was detected in the majority of SPNs, but only in a minority of pNENs ( <0.01). Hemorrhage occurred non -significantly more often in SPNs (p =0.09). Signal inhomogeneity in T1 -fat -saturated (p <0.01) and T2 -weighted imaging (p =0.046) as well as cystic degeneration (p <0.01) were more often observed in SPNs. Hyperenhancement in the arterial and portal -venous phase was more common in pNENs (p <0.01). Enlargement of locoregional lymph nodes (p <0.01) and liver metastases (p =0.03) were observed in some pNEN patients, but not in SPN patients. Multivariate logistic regression identified the presence of a capsule (p <0.01), absence of arterial hyperenhancement (p <0.01), and low patient age (p <0.01), as independent predictors for SPN. Conclusions: The present study provides three key features for differentiating SPNs from pNENs extracted from a large patient cohort: presence of a capsule, absence of arterial hyperenhancement, and low patient age.