Endoscopic ultrasound-guided fine-needle aspiration cytology in the diagnosis of intraductal papillary mucinous neoplasms of the pancreas. A study of 8 cases.

CONTEXT: Intraductal papillary mucinous neoplasm (IPMN) is an increasingly recognized neoplasm of the pancreas, accounting for 5% of pancreatic neoplasms, it is considered difficult to diagnose by fine-needle aspiration (FNA) cytology.

OBJECTIVE: The aim of this study was to investigate the role of EUS-guided FNA cytology in the diagnosis of IPMN of the pancreas.

PATIENTS: Eight cases of surgically proven IPMN with pre-operative endoscopic ultrasound-guided (EUS-guided) FNA cytology were collected for retrospective analysis.

MAIN OUTCOME MEASURES: EUS-FNA cytology was performed with the on-site attendance of a cytopathologist in all cases. EUS/clinical findings, macroscopic/microscopic features of cell blocks and smears, and immunocytochemical stains accompanied by histopathologic diagnosis were recorded and studied.

RESULTS: EUS revealed hypoechoic masses in the head of pancreas (n=6) and in the body/tail (n=2), measuring from 16.6 to 35.8 mm. In all cases, the hypoechoic mass had a distinctive distribution, involving the main pancreatic duct and/or the associated large branch ducts while intraductal nodules or multiple cysts were detected. Cytological specimens were characterized by a background containing abundant mucin in all cases and rarely by inflammation (neutrophils and histiocytes) (n=4). Neoplastic cells were entrapped in a mucinous background either single or loosely cohesive, and forming papillae in 7 cases. Mucinous epithelium was observed in all cases. Single atypical and irregular clusters were found in 3 cases (which were cytologically described as highly suggestive malignant IPMNs, and were histologically confirmed). Two cases were diagnosed as benign IPMN and, in 3 cases, the biological behavior was not easy to determine by cytology alone (histologically diagnosed as borderline). The histological diagnosis confirmed the FNA cytology diagnosis: 3 malignant IPMNs, 2 benign IPMNs and 3 borderline IPMNs. Immunostains were available in 5 out of 8 cases. Mucin 1 (MUC-1) was positive in 2 cases of malignant IPMN (histologically classified as null type ad intestinal type), mucin 2 (MUC-2) was positive in 3 cases (2 malignant both of the intestinal type, and 1 benign of the intestinal type I) and c-erbB2 was positive in 3 cases (2 benign - null and intestinal type - and 1 malignant null type).

CONCLUSIONS: The characteristic pre-operative EUS findings and cytomorphologic features, in addition to the immunocytochemical profile, were accurate indications and coincided with the final/post-operative histological diagnosis of IPMN.