Intraductal papillary mucinous tumors of the pancreas confined to secondary ducts show less aggressive pathologic features as compared with those involving the main pancreatic duct

Intraductal papillary mucinous tumors (IPMTs) of the pancreas are rare tumo rs characterized by a malignant potential. Because of the progress of imagi ng procedures, smaller cystic pancreatic lesions are now detected and some of them correspond to IPMTs that involve ectatic pancreatic branch ducts bu t spare the main pancreatic duct. To investigate differences in morphology and clinical behavior of branch and main duct types of IPMT, a surgical ser ies of 43 cases was studied. All pathologic specimens of IPMT, surgically r esected in our institution between October 1987 and July 1998, were analyze d. In all cases, the entire pancreatic specimen was systematically examined . IPMT of the branch type was found in 13 (30%) patients, whereas IPMT of m ain pancreatic duct type that involved the main pancreatic duct and branch ducts was observed in 30 (70%) patients. Patients with IPMT of the branch t ype were younger (median age, 55 yrs vs 64 yrs), and all but one of the les ions were located in the head and neck of the pancreas (vs 17 of 30 patient s with the main duct type). The size of the cysts ranged from 4 to 55 mm, a nd the major duct showed a mild dilation in most cases. in contrast to the main pancreatic duct type, which showed invasive carcinoma and in situ carc inoma in 11 (37%) of 30 patients and 6 (20%) of 30 patients, respectively, IPMT of the branch type showed significantly less aggressive histologic les ions with five (39%) patients with simple hyperplasia, six (46%) patients w ith atypical hyperplasia, and two (15%) patients with in situ carcinoma. No invasive carcinoma was observed in this group, IPMT of the branch type occ urs in younger patients and is associated with less aggressive histologic f eatures than is the main pancreatic duct type. Our findings raise the diffi cult issue of clinical management of IPMT of the branch type as a distincti ve group.