Clinical implication of morphological subtypes in management of intraductal papillary mucinous neoplasm

Morphological subtypes of intraductal papillary mucinous neoplasm (IPMN) have been established. Invasive IPMNs include colloid carcinoma and tubular carcinoma. Few studies have explored the association between the morphological and invasive subtypes in a large population. Clinical relevance of the morphological subtypes remains unclear.

One hundred sixty-nine consecutive patients who underwent curative resection of IPMN were enrolled. The intraductal components were classified into four distinct epithelial subtypes: gastric, intestinal, pancreatobiliary, and oncocytic. The invasive components were classified as colloid or tubular.

The numbers of patients with gastric, intestinal, pancreatobiliary, and oncocytic subtypes were 123, 42, 3, and 1, respectively. Fifty-six patients had invasive cancer (tubular type, 42; colloid type, 14). The proportions of gastric type IPMN within each histological grade were 88 % among adenomas, 43 % among noninvasive carcinomas, 41 % among minimally invasive carcinomas, and 74 % among invasive carcinomas. Gastric subtype was more commonly associated with branch duct type and intestinal subtype with main duct type, and these tendencies were statistically significant (P = 0.0131). Furthermore, there was a strong correlation between gastric and tubular types and between intestinal and colloid types (P < 0.0001). The 5-year survival rate among the 56 invasive cancers was 52.7 % for gastric type and 89.7 % for intestinal type, which was statistically significant (P = 0.030).

Gastric type IPMN is mostly derived from branch duct IPMN and often demonstrates benign behavior, as seen with adenomas. However, once gastric type IPMN develops into invasive carcinoma, the survival rate is significantly lower than other types.