Pancreatic juice cytology and subclassification of intraductal papillary mucinous neoplasms of the pancreas.

Objectives: Histological subclassification of intraductal papillary mucinous neoplasms (IPMNs) is important because the malignant potential of each subtype is different. We investigated whether pancreatic juice cytology can be used to define the subtypes of IPMNs preoperatively. Methods: The cytological findings and pathological parameters in 19 cases of IPMN were analyzed for correlations. Pancreatic juice cytology specimens were reviewed and classified into 4 types according to the criteria previously described for histological diagnosis: intestinal (Int), gastric foveolar (GF), oncocytic (Onc), and pancreatobiliary (PB), and the resected IPMNs were classified histologically using the same criteria for comparison. Immunochemical testing for MUC proteins was also performed. Results: In 15 cases (79%), the cytological and histological subclassifications were in agreement. The cytology specimens displayed different features corresponded to their histological subtypes. The sensitivities of the cytological diagnosis of each subtype were 80.0% (Int), 72.7% (GF), and 100% (Onc/PB); and the specificities were 85.7% (Int), 87.5% (GF), and 93.8% (Onc/PB). The cytoplasm of the Int-type cells in the pancreatic juice cytology specimens was positive for MUC2. Conclusions: Most of the cytological findings of IPMNs corresponded to the histological findings. The use of MUC2 immunocytochemistry in IPMN subtyping was also demonstrated. Subtyping of IPMNs is useful for preoperative evaluation in addition to cytomorphological grading.