Solid pseudopapillary neoplasms (SPNs) are very rare pathologic tumors of the pancreas, accounting for only 1-2% of all exocrine pancreatic tumors. This tumor is also known as Frantz's tumor, named after the author who first described its characteristics. Although various names have been used to describe this lesion, in 2010, it was finally included in the WHO classification of pancreatic tumors under the name of solid pseudopapillary neoplasm. SPNs predominantly affect young female patients. Despite it is often large in size, most are well circumscribed and surgical resection usually shows an excellent prognosis. It was reported that approximately 10e15% of cases of SPTs are malignant, but complete surgical resection of these tumors can result in long-term survival even in cases of distant metastasis and peritoneal seeding.
However, the origin of SPT is still controversial, and its clinical course is known to be unpredictable because both pathological and biological prognostic factors are non-specific for metastasis and recurrence (“surgical enigmas”).
Recently, the Korean Pancreatic Surgery Study Group performed a multicenter study of pancreatic SPNs to describe the clinicopathologic characteristics of pancreatic SPNs in Korea, to determine the long-term surgical results of patients who underwent resection, and to delineate the clinical features that can predict recurrence after SPT surgical resection. It finally showed microscopic malignant characteristics, large size tumor, and stage IV were clinically detectable parameters to predict the recurrence of SPNs after surgical treatment, suggesting the detailed pathological characterization in pathological examination.
How malignant is the SPN of the pancreas? This question may be very difficult to answer, because SPNs itself is very rare and most SPNs provide quite favorable long-term oncologic outcomes. The concept of “aggressive” SPNs is based on the extremely rare case report, and fails to define general characteristics of long-term oncologic outcome. We performed literature review-based statistical approach to delineate the characteristics of aggressive SPNs. In this presentation, our recent analysis to define the malignant potential of aggressive SPN of the pancreas will be discussed.

Reference
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One Hundred Twenty-One Resected Solid Pseudopapillary Tumors of the Pancreas: An 8-Year Single-Institution Experience at Zhongshan Hospital, Shanghai, China.Xu Y1, Zhao G, Pu N, Nuerxiati A, Ji Y, Zhang L, Rong Y, Lou W, Wang D, Kuang T, Xu X, Wu W. Pancreas. 2017 Sep;46(8):1023-1028.