Solid Pseudopapillary Neoplasms of the Pancreas: Evaluation of Diagnostic Utility of Endoscopic Ultrasound-Guided Fine Needle Aspiration (EUS-FNA)

Endoscopic ultrasound-guided fine needle aspiration (EUS-FNA) is an important and accurate modality for the diagnosis of solid and cystic lesions of the pancreas. The objectives of this retrospective study are to review the pertinent cytologic criteria for diagnosing SPNs and to evaluate the diagnostic utility of EUS-FNA. A total of 924 pancreatic FNAs were performed at our institution from January 2002 through February 2013. Of these, four cases (three females, mean age 17 years; one male, age 61 years) were identified with a diagnosis of SPN initially rendered on cytologic material obtained by EUS-FNA and subsequently confirmed by histopathologic examination of the resection specimen. No on site evaluation was conducted for any of these cases. Cytologic smears were assessed by two independent reviewers for the presence of the following diagnostic features: a highly cellular aspirate; the presence of myxoid or hyalinized fibrovascular stalks lined by neoplastic cells with pale to finely granular cytoplasm and indistinct cell borders; and monotonous, round to oval nuclei containing delicate granular nuclear chromatin, inconspicuous nucleoli, and nuclear grooves and inclusions. Cell block material was available for confirmatory immunohistochemical studies in one case. Three of the four cases were diagnosed as SPNs, and one was deemed to be a pancreatic endocrine neoplasm (islet cell tumor) on cytologic evaluation. Of the remaining three cases determined to be a SPN on cytology, two were confirmed histologically by review of available slides obtained from the surgical resection specimens. The most consistent cytologic features for diagnosing SPNs by EUS-FNA in our series was the presence of a highly cellular aspirate containing several hyalinized fibrovascular stalks lined by monotonous neoplastic cells with round to oval nuclei and nuclear grooves. We conclude that EUS-FNA is an accurate and effective diagnostic tool in the diagnosis of SPNs of the pancreas.