A case of small solid-pseudopapillary neoplasm (SPN) in a male preoperatively diagnosed by twice use of EUS-FNA

Abstract

A 42-year-old man was referred to our hospital because of mass lesion located in the pancreatic body. Contrast-enhanced CT scan showed a pancreatic body tumor 14mm in diameter, which was hypo dense in early phase and unclear in delayed phase. No capsules or cysts were identified. FDG-PET imaging showed increased uptake in the pancreatic body. We performed EUS-FNA for diagnosis. During the first attempt, we only recognized a few acinar cells leading to the second attempt. The second EUS-FNA material contained a few homogenous cell clusters different from normal pancreatic tissue, however, the clusters did not demonstrate typical pseudopapillary and/or pseudorosette structures frequently observed in SPNs. We suspected SPN because we identified eccentric nuclei and slightly eosinophilic cytoplasm often containing a small perinuclear vacuole. Immunostaining revealed that these cells were positive for β-catenin (abnormal nuclear expression) and CD10. So we preoperatively diagnosed it as SPN. We performed distal pancreatectomy and finally diagnosed it as SPN at the histopathological examination of the resected specimen. Even if an initial analysis did not show typical pseudopapillary structure, we should suspect SPN and perform further examination, including immunostaining, in cases where cells of unknown origin having remarkable intracytoplasmic vacuoles are detected.