Invasive Carcinoma Originating in an Intraductal Papillary Mucinous Neoplasm of the Pancreas

Abstract

Intraductal papillary mucinous neoplasm (IPMN) of the pancreas is an indolent neoplasm by nature; however, it sometimes acquires invasive potential and has been classified as invasive IPMN. The aim of the present study was to investigate the clinicopathologic difference between invasive IPMN and a common type of invasive ductal carcinoma of the pancreas. Eighteen patients with invasive IPMN underwent pancreatectomy between 1992 and 2004. Clinical, biochemical, and histopathologic factors were retrospectively analyzed. The resulting data were compared with those of 274 patients with a common type of pancreatic ductal carcinoma who underwent surgery during the same period. The total size of tumor of invasive IPMN, including cystic and invasive components, was statistically larger than that of a common type of invasive ductal carcinoma (62 vs 40 mm, P < 0.001), but the size of invasive component of invasive IPMN was smaller than that of a common type of invasive ductal carcinoma (21 vs 40 mm, P < 0.001). Negative lymph node metastases and relatively limited local tumor spreading were frequently observed in patients with invasive IPMN. On microscopic examination, the tumors infiltrating the surrounding tissue had a less invasive growth pattern, and a lower frequency of lymphatic invasion, venous invasion, and intrapancreatic neural invasion was also observed in patients with invasive IPMN. The 5-year survival rate of invasive IPMN was significantly higher than that of common-type invasive ductal carcinoma (42% vs 20%, P = 0.04). An increased awareness of invasive IPMN has enabled pancreatectomies to be performed at an earlier stage, relative to that for ordinary pancreatic cancer. The less frequent detection of pathological factors concerned with tumor invasiveness in patients with invasive IPMN suggested the lower aggressive behavior of this tumor.