Introduction
Solid-pseudopapillary neoplasm (SPN) is a rare tumor of low malignancy that occurs predominantly in young females. Imaging of SPN is often described as a well-defined and heterogeneous tumor with calcifications or cysts, otherwise small size SPN often shows a homogeneously solid tumor. However, the differential diagnosis between SPN and other cystic tumors is often difficult due to the variety of imaging findings. In this report, we describe the clinical features and preoperative diagnosis of SPN we experienced at our hospital.
Aims & Methods
We studied 18 cases of SPN that were pathologically diagnosed by surgical resection at our hospital between 1997 and 2022.
Results
There were 12 female and 6 male patients, with a median age of 39.5 years (range: 9-67) and a median tumor size of 23 mm (range: 9-66). The tumor location was in the pancreatic head in 4 cases, body in 6 cases, and tail in 8 cases. The median follow-up period was 89.5 months (range: 8-265), and recurrence-free survival was achieved in all cases during the follow-up period. The tumors were incidentally detected in 15 cases during health check-ups (mainly by ultrasonography) or other medical examinations, while the other 3 cases were detected due to subjective symptoms that were thought to be caused by SPN. SPN could be diagnosed by contrast-enhanced CT in 10 of 18 cases (56%) and by EUS in 7 of 12 cases (58%). Contrast-enhanced CT showed enhancing mass in 10 cases, cystic component in 9 cases (50%), and calcification in 8 cases (44%). Among the 8 cases in which SPN could not be diagnosed by contrast-enhanced CT, EUS was performed in 7 cases, and we could diagnose SPN in 2 cases. Both cases had small lesions of less than 13 mm without cystic components, which made the differentiation from other tumors difficult on contrast-enhanced CT, however EUS showed well-circumscribed, well-defined, and homogeneously hypoechogenic tumors. MRI was performed in 12 cases, and could diagnose SPN in 5 cases, but MRI did not improve the diagnostic accuracy compared to contrast-enhanced CT. The diagnostic accuracy of EUS-guided fine needle aspiration (EUS-FNA) was 89% (8/9 cases). There were 5 cases in which SPN could not be diagnosed preoperatively. Among them, 3 cases had small tumor sizes (12-16 mm), and 4 cases lacked calcification, making it difficult to differentiate them from neuroendocrine tumors or solid-cystic neoplasms.
Conclusion
Most cases of SPN are detected incidentally, and regular abdominal ultrasonography during medical check-ups is important for early detection. Diagnosis can be more difficult in cases with small tumor diameter, and no cystic component or calcification. However adding EUS to contrast-enhanced CT imaging may improve accuracy. Furthermore, EUS-FNA contributes to preoperative diagnosis with a high diagnostic accuracy.