Clinicopathologic Review of 31 Cases of Solid Pseudopapillary Pancreatic Tumors: Can We Use the Scoring System of Microscopic Features for Suggesting Clinically Malignant Potential?

A solid pseudopapillary tumor (SPT) is a pancreatic neoplasm of low malignant potential. The potentially malignant pathologic features of SPTs were regarded as angioinvasion, perineural invasion, deep invasion of the surrounding acinar tissue, and nuclear pleomorphism. We retrospectively reviewed 31 cases of SPTs (25 female and 6 male patients, with an average age of 35 ± 14 years). The mean follow-up period was 132.0 ± 55.9 months. To evaluate the clinical impact of above pathological parameters, we analyzed their correlation with actually observed clinical malignancy. In three cases, the SPTs were clearly clinically malignant: one patient had recurrences three times, one showed lymph node metastases, and one deep soft tissue invasion around the gastroduodenal artery. Tumor infiltration to the peripancreatic soft tissue was observed in 17 cases (54.8%). The pathologic features considered suggestive of malignant potential were angioinvasion (25.8%), perineural invasion (6.5%), presence of mitosis in 10 high-power fields (16.1%), and moderate nuclear pleomorphism (19.4%). The presence of at least three of these features was not correlated with clinically confirmed malignant behavior (P = 0.570). Microscopic pathologic features of SPTs cannot be reliably associated with aggressive clinical behavior. Moreover, the absence of these microscopic features cannot exclude clinical malignancy.