Cytology Adds Value to Imaging Studies for Risk Assessment of Malignancy in Pancreatic Mucinous Cysts

Objective: Evaluate the value of cytology relative to imaging features in risk assessment for malignancy as defined in the Sendai Guidelines. Background: The Sendai Guidelines list symptoms, cyst size > 30 mm, dilated main pancreatic duct (MPD) > 6 mm, mural nodule (MN) and "positive" cytology as high risk stigmata for malignancy warranting surgical triage. Methods: We reviewed clinical, radiological and cytological data of 112 patients with histologically confirmed mucinous cysts of the pancreas evaluated in a single tertiary medical center. Cytology slides were blindly rereviewed and epithelial cells grouped as either benign or high-grade atypia (HGA) [>= high-grade dysplasia]. Histologically, neoplasms were grouped as benign (low-grade and moderate dysplasia) and malignant (in situ and invasive carcinoma). Performance characteristics of cytology relative to other risk factors were evaluated. Results: Dilated MPD, MN, and HGA were independent predictors of malignancy (p < 0.0001), but not symptoms (p = 0.29) or cyst size > 30 mm (p = 0.51). HGA was the most sensitive predictor of malignancy in all cysts (72%) and in small (<= 30 mm) branch-duct intraductal papillary mucinous neoplasm (BD IPMN; 67%), whereas also being specific (85 and 88%, respectively). MN and dilated MPD were highly specific (> 90%), but insensitive (39%-44%). Cytology detected 30% more cancers in small cysts than dilated MPD or MN and half of the cancers without either of these high-risk imaging features. Conclusions: Cytology adds value to the radiological assessment of predicting malignancy in mucinous cysts, particularly in small BD IPMN.