American Surgical Association
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Intraductal Papillary Mucinous Neoplasms (IPMN): Factors Predicting Malignancy
Patrick B White*, Joshua A Waters*, Marshall Baker*, Oscar W Cummings*, Thomas J Howard*, Henry A Pitt, Nicholas J Zyromski*, Atilla Nakeeb*, Keith D Lillemoe, C. Max Schmidt*
Indiana University School of Medicine, Indianapolis, IN

OBJECTIVE: Surgical management of IPMN remains controversial. Predicting malignancy has proven difficult. Previous studies have classified lesions as operative/non-operative based upon size. We hypothesized that IPMN size, type, location and distribution predict malignancy.
METHODS: From 1991 to 2006, 215 patients with IPMN were treated and 151 patients underwent 158 operations. Analysis was performed on cytology, pathology, and radiology. Utilizing MRI/MRCP, CT, and ERCP, detailed classification of type, location, distribution and size was performed.
RESULTS: Malignant (invasive/in-situ-carcinoma) IPMN accounted for 32% of which 17% were invasive. Branch-type had the lowest incidence of invasion (14%) followed by mixed-type (23%), and main duct-type (50%). Multifocal IPMN were identified in 52% of which invasion was identified in 9% of branch-types and 26% of mixed-types. Branch-type lesions of neck, body and tail were invasive in 25-29% while head lesions were invasive in only 7% (p<0.05). Branch-types <2cm were invasive in 15% whereas lesions >2cm were invasive in 14%. Branch-type cross-sectional area was smaller in invasive (406±143mm2(mean±SEM)) versus noninvasive (517±79mm2) lesions but failed to reach significance (p=0.6). Main duct diameter was greater in malignant (9.4 mm) than in benign disease (5.9mm) (p<0.01).
CONCLUSIONS: In contrast to previous studies, IPMN size does not positively correlate with malignancy or invasion. In branch-type, multifocality and pancreatic head location is associated with less invasion, possibly due to earlier presentation. In accordance with previous studies, main duct-type IPMN is a strong predictor of malignancy. Lesion size should be used cautiously as a predictor of invasion in IPMN.

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