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Recently, attention has been drawn to papillary neoplasm of the pancreatobiliary systems. In the pancreas, the disease entity of intraductal papillary mucinous neoplasm (IPMN-P) is widely recognized. In contrast, the pathological characteristics of biliary papillary tumors, such as biliary papilloma(tosis) and papillary cholangiocarcinoma, have not yet been well documented. In this study, we compared the pathological features and post-operative prognosis among biliary papillary tumors (10 cases of biliary papilloma(tosis) and 22 cases of papillary cholangiocarcinoma), conventional non-papillary cholangiocarcinoma (15 cases), and IPMN-P (31 cases). Macroscopically, all biliary papillary tumors were characterized by the prominent intraductal papillary proliferation, and macroscopic mucin-hypersecretion was seen in 9 of 32 cases (28%). Histologically, biliary papillary tumors consisted of three types of tumor cells (pancreaticobiliary, intestinal and gastric types), whereas only the pancreaticobiliary type was observed in non-papillary cholangiocarcinoma. Immunohistochemically, biliary papillary tumors were characterized by the common expression of MUC2, CDX2 and cytokeratin 20. In addition, biliary papillary tumors could be associated with two types of invasive lesions: tubular adenocarcinoma (9 cases) and mucinous carcinoma (5 cases). Patients with tubular adenocarcinoma had a poor prognosis compared to non-invasive papillary tumor or papillary tumor with mucinous carcinoma. These pathological characteristics and the survival status of biliary papillary tumors were different from those of non-papillary cholangiocarcinoma, and rather closely resembled those of IPMN-P. C ertain types of papillary tumors with different malignant potentials are known to occur in the intrahepatic and extrahepatic bile ducts. 1 Biliary papilloma (papilloma adenoma) is a rare benign neoplasm composed of papillary proliferation of the dysplastic biliary epithelium with delicate fibrovascular stalks. 1 Multiple recurring biliary papillomas are known as biliary papillomatosis. Some cases of biliary papillomatosis have multiple tumors at the same time, and others manifest asynchronous tumors at different sites of the biliary tract. 1,2 Biliary papilloma and papillomatosis are now thought to be pre-malignant lesions, and they have the potential to progress to invasive lesions via an adenomacarcinoma sequence. 3 Some cholangiocarcinomas show mainly papillary proliferation in the bile duct lumen, and those cases are designated as papillary cholangiocarcinoma (papillary-CC)

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Recently, much attention has focused on IgG4-related disease, which is characterized by abundant IgG4-positive plasma cell infiltration and high serum IgG4 levels. IgG4-related disease sometimes manifests as tumorous lesions, and its relationship to inflammatory pseudotumor has been suggested. In this study, we examined clinicopathological features of a total of 16 cases of hepatic inflammatory pseudotumor (11 men and 5 women with an average age of 67 years) with respect to IgG4-related disease. The tumors could be pathologically classified into two types: fibrohistiocytic (10 cases) and lymphoplasmacytic (6 cases). Fibrohistiocytic inflammatory pseudotumors were characterized by xanthogranulomatous inflammation, multinucleated giant cells, and neutrophilic infiltration, and mostly occurred in the peripheral hepatic parenchyma as mass-forming lesions. In contrast, lymphoplasmacytic inflammatory pseudotumors showed diffuse lymphoplasmacytic infiltration and prominent eosinophilic infiltration, and were all found around the hepatic hilum. In addition, venous occlusion with little inflammation and cholangitis without periductal fibrosis were frequently observed in the fibrohistiocytic type, whereas obliterative phlebitis and cholangitis with periductal fibrosis were common features of the lymphoplasmacytic type. Interestingly, IgG4-positive plasma cells were significantly more numerous in the lymphoplasmacytic than fibrohistiocytic type. However, two of the fibrohistiocytic inflammatory pseudotumors had relatively many IgG4-positive plasma cells. In conclusion, hepatic inflammatory pseudotumor could be classified into two types based on clinicopathological characteristics. The lymphoplasmacytic type is unique, and could belong to the so-called IgG4-related diseases. In contrast, the fibrohistiocytic type might still be a heterogeneous group of disorders. This latter type seems pathologically different from IgG4-related disease, although cases with relatively abundant IgG4-positive plasma cells should be differentiated from IgG4-related disease with secondary histopathologic modifications.

Biliary cystic tumors, which are also called biliary cystadenoma and cystadenocarcinoma, are thought to be a heterogeneous disease entity, and some of them are known to show a luminal communication to the bile duct. In this study, we examined the clinicopathological features of nine cases of biliary cystic tumors with bile duct communication. They were composed of five males and four females with an average age of 67 years (52-84 years). They were multilocular (eight cases) or unilocular (one case), and all cases contained mucinous fluid. A direct luminal communication with the bile ducts was identified in five cases on preoperative or intraoperative cholangiographies. Biliary cystic tumors examined in this study were histologically adenoma (one case), adenocarcinoma in situ (six cases), and adenocarcinoma associated with microinvasive mucinous carcinoma (two cases). One case of adenocarcinoma in situ also had the adenoma component (adenocarcinoma in adenoma). Dysplastic mucinous epithelium proliferated in flat, micropapillary and papillary fashions within the intracystic spaces. Intraepithelial neoplasm was observed within non-dilated adjacent bile ducts, suggesting a direct luminal communication between the cystic tumors and the bile duct. Ovarian-like stroma was not observed in their walls in any cases. Immunohistochemically, seven cases expressed MUC1 or MUC2 in the neoplastic biliary epithelium. All cases except one were alive without any evidences of tumor recurrence after total excision (3-156 months after surgery). These clinicopathological features resembled those of intraductal papillary neoplasm of the bile duct, which had been reported as a biliary counterpart of pancreatic intraductal papillary mucinous neoplasm. In conclusion, biliary cystic tumors with bile duct communication could be regarded as intraductal papillary neoplasm with a prominent cystic dilatation of the bile duct and mucin retention, rather than true biliary cystic neoplasms.

A subgroup of peripheral CCs with an infiltrating replacement growth pattern resembles reactive bile ductules and expresses NCAM. 'Bile ductular carcinoma' may be a better term for this subgroup.

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In this study, we examined the possible involvement of progenitor cells in the carcinogenesis of human hepatocellular carcinoma (HCC) using tissue specimens and cell lines. We used ATP-binding cassette transporter ABCG2 as a progenitor cell marker. Immunohistochemically, ABCG2؉ hepatocytes were observed in the periportal areas of the dysplastic nodule, and ABCG2؉ cancer cells were also scattered or focally clustered in HCC. We sorted the cultured HCC cells (HuH7 and PLC5) into ABCG2