Background & Aims: Mucin-producing neoplasms (MPNs) of the pancreas include mucinous cystic neoplasms (MCNs) and main-duct, branch-duct, and combined intraductal papillary mucinous neoplasms (IPMNs). MCNs and branch-duct IPMNs are frequently confused; it is unclear whether main-duct, combined, and branch-duct IPMNs are a different spectrum of the same disease. We evaluated their clinical and epidemiologic characteristics. Methods: Patients who underwent resection for histologically confirmed MPNs were identified (N = 557); specimens were reviewed and eventually reclassified. Results: One hundred sixty-eight patients (30%) had MCNs, 159 (28.5%) had branch-duct IPMNs, 149 (27%) had combined IPMNs, and 81 (14.5%) had main-duct IPMNs. Patients with MCNs were significantly younger and almost exclusively women; 44% of patients with main-duct or combined IPMNs and 57% of those with branch-duct IPMNs were women. MCNs were single lesions located in the distal pancreas (95%); 11% were invasive. IPMNs were more frequently found in the proximal pancreas; invasive cancer was found in 11%, 42%, and 48% of branch-duct, combined, and main-duct IPMNs, respectively (P = .001). Patients with invasive MCN and those with combined and main-duct IPMNs were older than those with noninvasive tumors. The 5-year disease-specific survival rate approached 100% for patients with noninvasive MPNs. The rates for those with invasive cancer were 58%, 56%, 51%, and 64% for invasive MCNs, branch-duct IPMNs, main-duct IPMNs, and combined IPMNs, respectively. Conclusions: MPNs comprise 3 different neoplasms: MCNs, branch-duct IPMNs, and main-duct IPMNs, including the combined type. These tumors have specific clinical, epidemiologic, and morphologic features that allow a reasonable degree of accuracy in preoperative diagnosis.
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