Intraductal tubulopapillary neoplasm of the pancreas on fine needle aspiration: case report with differential diagnosis.

Intraductal tubulopapillary neoplasm (ITPN) is a rare primary pancreatic neoplasm accounting for less than 1% of all pancreatic exocrine neoplasms and 3% of intraductal neoplasms of the pancreas. Data on this entity are still limited. Here, we report a case of ITPN with cytopathologic and histopathologic findings. A 41-year-old woman with a 2.2 cm cyst in the head of the pancreas for five years was referred to our institution. The endoscopic ultrasound-guided fine-needle aspiration produced cytospins were moderately cellular with a few fragments of markedly atypical epithelium. The neoplastic cells displayed high-grade nuclear atypia with enlarged, eccentric nuclei, anisonucleosis and prominent nucleoli, irregular nuclear membranes, high nucleus to cytoplasmic (N/C) ratios, and a moderate amount of cytoplasm with no intracytoplasmic mucin. Histologically, the lesion was found to be an ITPN with focal high-grade dysplasia. No invasive carcinoma was identified. The neoplastic cells exhibited luminal immunolabeling for MUC-1, but were negative for MUC-2, trypsin, chymotrypsin, and P53. Approximately 5% of the neoplastic cells showed Ki-67 immunoreactivity. ITPN of pancreas may be a source of markedly atypical epithelial cells in pancreatic cystic aspiration. Clinical and radiographic findings, molecular mutational analysis, in combination with cytological features are essential to differentiate it from other disease entities.