Long-term clinical outcome of the surgically resected intraductal papillary neoplasm of the bile duct
Intraductal papillary neoplasm of the bile duct (IPNB) is a biliary neoplasm with predominant intraductal papillary growth and various degrees of malignant transformation. Although IPNB has been recently added to the WHO classification, the classification system needs refinements. We retrospectively reviewed 93 non-invasive and invasive IPNB cases, surgically resected from 1996 to 2006. To further characterize their biologic behavior, we modified the WHO classification into a 4-tier category system in which non-invasive IPNB cases with complex fused or cribriform papillae were separately designated. Epithelial types such as intestinal, gastric, pancreatobiliary, and oncocytic type were determined by morphology and mucin core protein immunohistochemistry. Resection margins were classified based on their microscopic appearances. The prognostic values of mucinous histology and MUC1 protein expression were also determined. IPNB with complex fused or cribriform papillae showed a worse prognosis than IPNB with simple papillae and one such case showed a metachronous metastasis. In addition, a positive surgical margin including dysplasia was associated with worse outcomes. Among the invasive IPNB cases, MUC1-positive tumors were more aggressive than MUC1-negative tumors. We propose that non-invasive IPNB with complex fused or cribriform papillae might be better classified as mucosa-confined cholangiocarcinoma rather than IPNB with high grade dysplasia. In addition, aggressive further resection is recommended when a positive surgical margin including dysplasia is reported during intraoperative histopathological evaluation.