Solid-pseudopapillary neoplasm of the pancreas: Cytomorphologic findings and literature review

Background: Solid-pseudopapillary neoplasm (SPN) is a rare pancreatic malignancy with an excellent prognosis. It is most commonly diagnosed in young women. This article comprehensively reviews the clinical, pathological and radiological features of this neoplasm, as well as its clinical management. Methods: A literature review of SPN was performed of all articles published in the English language in PubMed prior to November 1, 2013. Cytomorphological features, histopathology, immunohistochemistry, patient general demographics, molecular studies, radiologic imaging and clinical management were reviewed. Results: SPN displays distinct cytomorphological features on fine-needle aspiration - thin, delicate, branching vessels in a 'Chinese character' pattern lined by one to several layers of loosely cohesive neoplastic cells. Nuclear features include indented or grooved nuclei with an evenly distributed chromatin pattern and small inconspicuous nucleoli. SPN is characteristically immunoreactive for CD10, β-catenin (in an abnormal nuclear pattern), CD99 in a perinuclear dot-like pattern, a1-antitrypsin, and progesterone receptor. Almost all SPNs harbor an activating point mutation in exon 3 of the β-catenin gene (CTNNB1) . Clinicopathological features generally do not correlate with prognosis, and most patients experience excellent longterm survival. Conclusions: SPN can mimic other neoplasms of the pancreas, which can lead to diagnostic challenges in a limited cytologic specimen. Distinct cytomorphological features can help distinguish SPNs from other pancreatic neoplasms. Complete surgical resection as well as resection of metastatic disease is preferred given a low rate of tumor recurrence and long periods of disease-free intervals.