Cystic Pancreatic Endocrine Tumors An Endoscopic Ultrasound-guided Fine-Needle Aspiration Biopsy Study With Histologic Correlation

BACKGROUND: Cystic pancreatic endocrine tumors (PETS) are rare neoplasms with a preoperative diagnostic challenge. The aim of this study was to evaluate the preoperative diagnostic strategy for these tumors and to assess the clinical and pathologic characteristics. METHODS: Six cases of cystic PET were retrospectively enrolled. Endoscopic ultrasound-guided fine-needle aspiration biopsy (EUS-FNAB) was performed in 4 cases. All cytomorphologic data from conventional smears, ThinPrep preparations, and cell block preparations were reported in detail. RESULTS: There were 3 male and 3 female patients with a mean age of 52.3 years. Tumor size ranged from 10 mm to 60 mm (mean, 29.8 mm). EUS-FNAB contributed to an accurate diagnosis in all cases. Cytologically, loosely cohesive aggregates and single cells were predominant. Cells were small and typically plasmacytoid, with occasional cytoplasmic vacuolization. Nuclei were round or oval, uniform, with finely and evenly distributed chromatin. Immunocytochemistry confirmed the endocrine differentiation. Histologic findings were typical for endocrine proliferation. All tumors were well differentiated. CONCLUSIONS: Cystic PET is an unusual finding that presents diagnostic challenges for both endoscopists and cytologists. EUS-FNAB with the Thinprep preparation technique and cell block material were found to be helpful in improving diagnostic accuracy. Immunocytochemical staining with endocrine markers confirmed the diagnosis. Cancer (Cancer Cytopathol) 2009;117:203-10. (C) 2009 American Cancer Society.