A case of aggressive solid pseudopapillary neoplasm: Comparison of clinical and pathologic features with non-aggressive cases.

Solid pseudopapillary neoplasms (SPNs) may have an aggressive clinical course, but clinical predictors of this condition have not been thoroughly evaluated. We performed a retrospective study of 11 cases of SPN managed in our hospital between January 2007 and April 2015. Of these 11 cases, we encountered a single case with an aggressive clinical course. Histological, immunohistochemical, and clinical features were compared to identify predictors of poor prognosis. The 11 patients comprised four women and seven men with a median age of 41 years (range, 26-58 years). Clinical symptoms were nonspecific and the median tumor size was 4.6 cm (range, 1.4-18 cm). The patient with an aggressive clinical course developed multiple liver metastases within three months and died seven months after surgery. Pathological features of the tumor in this case included lymph node metastases, a diffuse growth pattern, extensive tumor necrosis, high mitotic rate, and immunohistochemistry. These features were not observed in patients who survived without recurrence at a median follow-up of 25 months (range, 6-82 months). Characteristic pathological features and a high proliferative index, as assessed by Ki-67 staining, may predict poor outcome in cases of SPN.