Intraductal papillary neoplasm of the bile duct

Intraductal papillary neoplasm of the bile duct (IPNB) is a variant of bile duct carcinoma that is characterized by intraductal growth and better outcomes compared with common cholangiocarcinoma. IPNBs are mainly found in patients from Far Eastern areas, where hepatolithiasis and clonorchiasis are endemic. According to the immunohistochemical profiles of the mucin core proteins, IPNBs are classified into four types: pancreaticobiliary, intestinal, gastric, and oncocytic. Approximately 40%-80% of IPNBs contain a component of invasive carcinoma or tubular or mucinous adenocarcinoma, suggesting that IPNB is a disease with high potential for malignancy. It is difficult to make an accurate preoperative diagnosis because of IPNB’s low incidence and the lack of specificity in its clinical manifestation. The most common abnormal preoperative imaging findings of IPNB are intraductal masses and the involvement of bile duct dilation. Simultaneous proximal and distal bile duct dilation can be detected in some cases, which has diagnostic significance. Cholangiography and cholangioscopy are needed to confirm the pathology and demonstrate the extent of the lesions. However, pathologic diagnosis by biopsy cannot reflect the actual stage in many cases because different foci may be of different stages and because mixed pathologic findings may exist in the same lesion. Surgical resection is the major treatment. Systematic cholangioscopy with staged biopsies and frozen sections is recommended during resection to ensure that no minor tumors are left and that curative resection is achieved. Staging, histologic subtype, curative resection and lymph node metastasis are factors affecting long-term survival.

Pathological classification of intrahepatic cholangiocarcinoma based on a new concept

Intrahepatic cholangiocarcinoma (ICC) arises from the lining epithelium and peribiliary glands of the intrahepatic biliary tree and shows variable cholangiocytic differentiation. To date, ICC was largely classified into adenocarcinoma and rare variants. Herein, we propose to subclassify the former, based on recent progress in the study of ICC including the gross classification and hepatic progenitor/stem cells and on the pathological similarities between biliary and pancreatic neoplasms. That is, ICC is classifiable into the conventional (bile duct) type, the bile ductular type, the intraductal neoplasm type and rare variants. The conventional type is further divided into the small duct type (peripheral type) and large bile duct type (perihilar type). The former is a tubular or micropapillary adenocarcinoma while the latter involves the intrahepatic large bile duct. Bile ductular type resembles proliferated bile ductules and shows a replacing growth of the hepatic parenchyma. Hepatic progenitor cell or stem cell phenotypes such as neural cell adhesion molecule expression are frequently expressed in the bile ductular type. Intraductal type includes papillary and tubular neoplasms of the bile duct (IPNBs and ITNBs) and a superficial spreading type. IPNB and ITNB show a spectrum from a preneoplastic borderline lesion to carcinoma and may have pancreatic counterparts. At invasive sites, IPNB is associated with the conventional bile duct ICC and mucinous carcinoma. Biliary mucinous cystic neoplasm with ovarian-like stroma in its wall is different from IPNB, particularly IPNB showing cystic dilatation of the affected ducts. Rare variants of ICC include squamous/adenosquamous cell carcinoma, mucinous/signet ring cell carcinoma, clear cell type, undifferentiated type, neuroendocrine carcinoma and so on. This classification of ICC may open up a new field of research of ICC and contribute to the clinical approach to ICC.