[1598] IPMNS of the Pancreas and Associated Small Duct Lesions – Analysis of the Distribution of High Grade Dysplasia.

Gloria Q Young, Nora Katabi, Efsevia Vakiani, Umesh K Bhanot, David S Klimstra. Memorial Sloan-Kettering Cancer Center, New York, NY

Background: Pancreatic intraductal papillary mucinous neoplasms (IPMNs) are preinvasive neoplastic lesions that are increasingly recognized. IPMNs can be associated with small ductal lesions (SDL), both close to and distant from the main cystic lesion (MCL). The differential diagnosis of SDLs includes pancreatic intraepithelial neoplasia (PanIN), which often demonstrates similar histologic features. In some cases the degree of dysplasia may vary throughout all of the intraductal neoplasia, but the relevance of the degree of dysplasia in SDLs has not been addressed. Our goal was to evaluate IPMNs with associated SDLs, comparing their morphologic features to determine if a relationship exists.
Design: Among 46 reviewed cases of IPMNs, 18 cases were identified with SDLs separately identified from the MCL (39%). Only cases lacking an invasive carcinoma component were selected. Clinical information was retrieved. Histologic analysis of the MCL, the SDLs, and margin sections was performed.
Results: Half of the IPMNs were located in the pancreatic head. The size ranged from 0.4-8.0 cm, (mean, 2.99 cm). 56% (n=10) were branch duct type, and the remainder were either main duct type or combined type. 72% of IPMNs (n=13) had gastric type (GT) epithelium, while intestinal and pancreatobiliary types numbered 3 and 2, respectively. 78% (14/18) cases had high grade dysplasia (HGD) somewhere in the pancreas, and among these, 9 cases (64%) showed HGD in the MCL, while 5 cases (36%) showed HGD only in the SDLs. All cases with a higher grade of dysplasia in the SDLs versus the MCL were GT IPMNs. Evaluation of the margin showed 2 cases with HGD, 7 with moderate dysplasia and 6 with low grade dysplasia. Margin section slides were not available for 3 cases. IPMN was favored at the margin in 3/15 cases, PanIN was favored at the margin in 6/15 cases, while 6/15 cases were deemed indeterminate for IPMN vs. PanIN.
Conclusions: IPMNs can be associated with SDLs and the interpretation of these smaller lesions can be difficult. In 36% of cases, a higher grade of dysplasia was found in SDLs than in the MCL. Whether SDLs are an extension of the IPMN or separate foci of PanIN is difficult to determine by morphology alone. This problem is often encountered in the evaluation of resection margins; in 40% of cases, margin status remained indeterminate. IHC and molecular studies may help in accurately classifying these lesions. The finding of higher grades of dysplasia in non-cystic ducts away from the MCL has implications for sampling of these specimens.
Category: Liver & Pancreas

Tuesday, March 1, 2011 1:00 PM

Poster Session IV # 198, Tuesday Afternoon


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