Prognostic Factors for Distal Bile Duct Carcinoma After Surgery.

BACKGROUND: Distal bile duct carcinoma continues to be one of the most difficult cancers to manage in terms of staging and radical resection. Pancreaticoduodenectomy (PD) with regional lymph node dissection has become the standard treatment of distal bile duct carcinoma. We evaluated treatment outcomes and histological factors in patients with distal bile duct carcinoma. METHODS: Seventy-four cases of resection of carcinoma of the distal bile ducts treated at our department during the period from January 2002 and December 2016 using PD and regional lymph node dissection as the standard surgical procedure were investigated. Survival rates of factors were analyzed using uni- and multivariate analyses. RESULTS: The median survival time was 47.8 months. On univariate analysis, age of 70 years or older, histologically pap, pPanc2,3, pN1, pEM0, v2,3, ly2,3, ne2,3 and postoperative adjuvant chemotherapy were statistically significant factors. On multivariate analysis, histologically pap was identified as a significant independent prognostic factor. The multivariate analysis identified age of 70 years or older, pEM0, ne2,3 and postoperative adjuvant chemotherapy as showing a significant trend towards independent prognostic relevance. CONCLUSION: The good news about resected distal bile duct carcinoma is that the percentage of those who achieved R0 resection has risen to 89.1%. Our multivariate analysis identified age of 70 years or older, pEM0, ne2,3 and postoperative adjuvant chemotherapy as prognostic factors. In order to improve the outcome of treatment, it is necessary to improve preoperative diagnostic imaging of pancreatic invasion and lymph node metastasis, establish the optimal operation range and clarify whether aortic lymph node dissection is needed to control lymph node metastasis, and establish effective regimens of chemotherapy.

[A case of hemobilia due to the rupture of pancreaticoduodenal artery aneurysm with choledocholithiasis].

A 79-year-old male patient had a huge choledocholithiasis that was difficult to remove and underwent endoscopic retrograde biliary drainage. He complained of hematemesis upon admission to our hospital. Endoscopic retrograde cholangiography showed bleeding from the papilla of Vater and revealed an upper filling defect with a large stone in the common bile duct. Furthermore, computed tomography detected an aneurysm close to the stone. Considering the occurrence of a ruptured pancreaticoduodenal artery aneurysm, we diagnosed this condition as hemobilia. Through angiography, we also detected a saccular aneurysm in the posterior superior pancreaticoduodenal artery (PSPDA);subsequently, selective transcatheter arterial embolization (TAE) was performed. However, bleeding persisted after TAE;therefore, we performed second-time embolization for other PSPDA branches. Consequently, hemostasis was achieved. To date, bleeding has not reoccurred. The pancreaticoduodenal artery constitutes a complex arcade;hence, cases of extremely difficult hemostasis by embolization have been reported. Herein, we have presented a life-saving case of choledocholithiasis treated with TAE for biliary bleeding from a PSPDA aneurysm rupture.

[A Vesected Case of Pancreatic Metastasis from Breast Cancer Which Recurred Six Years after Breast Surgery].

A 43-year-old woman who underwent surgical resection of invasive ductal carcinoma in the left breast at the age of 37 years old presented at our hospital for evaluation of pancreatic tumor. The original tumor was estrogen receptor(ER)progesterone receptor(PgR)and HER2 positive. At that time, she underwent radical mastectomy with no evident nodal disease. Postoperatively, the patient was placed on adjuvant tamoxifen therapy for several years. Six years following the original diagnosis of breast cancer, she was referred to the hospital for routine check-up while asymptomatic. Follow-up examination showed a solitary hypodense mass approximately 0.9 cm in size in the pancreas body on dynamic CT scan. The patient underwent a standard distal pancreatectomy with standard regional lymphadenectomy. Histopathological examination and immunohistochemical features revealed that the tumor was compatible with metastatic pancreatic adenocarcinoma from breast cancer.

Ex vivo magnifying endoscopic observation of bile duct mucosa using narrowband imaging.

BACKGROUND: Detailed endoscopic findings of the bile duct mucosa have not been fully established. This fundamental ex vivo study assesses the relationship between magnified endoscopic findings and pathological findings of the bile duct mucosa. METHODS: Forty-one surgically resected common bile duct mucosae were investigated. Each common bile duct was cut open longitudinally for ex vivo endoscopic observation. A magnifying endoscope commonly used for the gastrointestinal tract was used, using both white light imaging and narrowband imaging. After pathological diagnosis, the association between the magnifying endoscopic findings and histopathology was evaluated. RESULTS: Totally, 39 non-neoplastic mucosae and 13 neoplastic mucosae were evaluated. In 13 non-neoplastic mucosae without inflammation, an oval-shaped depressed area and a fine, regular network of microvessels were observed. These findings were not clearly seen or not seen at all in the non-neoplastic mucosae with inflammation. Although vessels with loop-like structure were observed on all eight papillary tumors of 13 neoplastic mucosae, no characteristic vessels were seen on the other five. CONCLUSIONS: Ishida and colleagues assessed the association between magnifying endoscopic findings and histopathological findings of the bile duct mucosa ex vivo. Oval-shaped, depressed areas and a fine, regular network of microvessels are characteristic features of normal bile duct mucosa, while loop structures may be indicative of a type of tumor vessel.

Marked accumulation of fluorodeoxyglucose and inflammatory cells expressing glucose transporter-3 in immunoglobulin G4-related autoimmune hepatitis.

Immunoglobulin (Ig)G4-related autoimmune hepatitis (AIH) is a recently proposed subtype that responds well to steroid treatment; however, its pathogenesis remains unclear. We report here a 65-year-old Japanese woman with skin itching and lip swelling. She had liver injury with jaundice, which persisted despite stopping anti-allergic agents. Blood chemistry revealed highly elevated serum IgG and IgG4 (535 mg/dL) levels, and positive anti-nuclear antibody. The diagnosis of AIH was based on liver biopsy. Notably, the IgG4+ /IgG+ cell ratio was 85%. On fluorodeoxyglucose (FDG) positron emission tomography/computed tomography, robust signal intensity was found in the liver, and in enlarged lymph nodes and salivary glands with confirmed IgG4+ cell infiltration. Immunofluorescence analysis of the liver biopsy specimen indicated clear expression of glucose transporter-3 (Glut-3) in IgG4+ inflammatory cells infiltrating into the portal area. This is the first report of simultaneous strong accumulation of FDG and Glut-3 expression in IgG4-related AIH, which might aid in elucidating the pathogenesis of this disease.

A case of pancreatic neuroendocrine tumor with multiple cystic components of various sizes.

The patient was a 51-year-old woman who, while undergoing a thorough health checkup, was found to have a tumor (measuring 60 mm in diameter) in the tail of the pancreas by abdominal ultrasonography. Contrast-enhanced computed tomography revealed delayed contrast enhancement; the tumor also contained numerous low-absorption areas showing poor contrast enhancement. On magnetic resonance imaging, the tumor was visualized as having high signal intensity areas inside the tumor on T2-weighted images. Positron emission tomography revealed an abnormal accumulation in the area corresponding to the tumor. Endoscopic ultrasonography (EUS) revealed a relatively hyperechoic solid area, with a number of echo-free areas of various sizes that assumed a honeycomb appearance. EUS-guided fine needle aspiration was carried out targeting the solid area within the tumor, which led to a diagnosis of pancreatic neuroendocrine tumor (PNET). Histopathological examination of the resected specimen revealed that the tumor was composed of numerous cysts of various sizes and solid components. The cysts contained no evidence of necrosis or bleeding. Immunohistochemically, the cystic as well as solid components were CD56 (+), synaptophysin (+) and chromogranin A (+) with MIB1 labeling index of 5%. On the basis of these findings, the final diagnosis was PNET (G2).

Muscle RAS oncogene homolog (MRAS) recurrent mutation in Borrmann type IV gastric cancer.

The prognosis of patients with Borrmann type IV gastric cancer (Type IV) is extremely poor. Thus, there is an urgent need to elucidate the molecular mechanisms underlying the oncogenesis of Type IV and to identify new therapeutic targets. Although previous studies using whole-exome and whole-genome sequencing have elucidated genomic alterations in gastric cancer, none has focused on comprehensive genetic analysis of Type IV. To discover cancer-relevant genes in Type IV, we performed whole-exome sequencing and genome-wide copy number analysis on 13 patients with Type IV. Exome sequencing identified 178 somatic mutations in protein-coding sequences or at splice sites. Among the mutations, we found a mutation in muscle RAS oncogene homolog (MRAS), which is predicted to cause molecular dysfunction. MRAS belongs to the Ras subgroup of small G proteins, which includes the prototypic RAS oncogenes. We analyzed an additional 46 Type IV samples to investigate the frequency of MRAS mutation. There were eight nonsynonymous mutations (mutation frequency, 17%), showing that MRAS is recurrently mutated in Type IV. Copy number analysis identified six focal amplifications and one homozygous deletion, including insulin-like growth factor 1 receptor (IGF1R) amplification. The samples with IGF1R amplification had remarkably higher IGF1R mRNA and protein expression levels compared with the other samples. This is the first report of MRAS recurrent mutation in human tumor samples. Our results suggest that MRAS mutation and IGF1R amplification could drive tumorigenesis of Type IV and could be new therapeutic targets.

ARHGEF15 overexpression worsens the prognosis in patients with pancreatic ductal adenocarcinoma through enhancing the motility and proliferative activity of the cancer cells.

BACKGROUND: Pancreatic ductal adenocarcinoma (PDAC) is one of the most aggressive neoplastic diseases, associated with a remarkably poor prognosis. However, the molecular mechanisms underlying the development of PDAC remain elusive. The aim of this study was to identify genes whose expressions are correlated with a poor prognosis in PDAC patients, and to unravel the mechanisms underlying the involvement of these genes in the development of the cancer. METHODS: Global gene expression profiling was conducted in 39 specimens obtained from Japanese patients with PDAC to identify genes whose expressions were correlated with a shorter overall survival. The effect of gene silencing or overexpression of ARHGEF15 in pancreatic cancer cell lines was examined by introducing siRNAs of ARHGEF15 or the ARHGEF15 expression vector. After assessing the effect of ARHGEF15 deregulation on the Rho-family proteins by pull-down assay, wound healing, transwell and cell viability assays were carried out to investigate the cellular phenotypes caused by the perturbation. RESULTS: The global mRNA expression profiling revealed that overexpression of ARHGEF15, a Rho-specific GEF, was significantly associated with a poor prognosis in patients with PDAC. We also found that the depletion of ARHGEF15 by RNA interference in pancreatic cancer cell lines downregulated the activities of molecules of the Rho signaling pathway, including RhoA, Cdc42 and Rac1. Then, we also showed that ARHGEF15 silencing significantly reduced the motility and viability of the cells, while its overexpression resulted in the development of the opposite phenotype in multiple pancreatic cancer cell lines. CONCLUSION: These data suggest that upregulation of ARHGEF15 contributes to the development of aggressive PDAC by increasing the growth and motility of the pancreatic cancer cells, thereby worsening the prognosis of these patients. Therefore, ARHGEF15 could serve as a novel therapeutic target in patients with PDAC.

Des-γ-carboxyprothrombin (DCP) and NX-DCP expressions and their relationship with clinicopathological features in hepatocellular carcinoma.

AIM: Des-γ-carboxyprothrombin (DCP) has been used as a tumor marker for hepatocellular carcinoma (HCC). Recently the DCP/NX-DCP ratio, calculated by dividing DCP by NX-DCP, has been reported useful in detecting HCC. The purpose of this study is to clarify the significance of DCP and NX-DCP expression in HCC tissues. METHODS: HCC and non-HCC tissue samples were obtained from 157 patients and were immunohistochemically examined for DCP and NX-DCP expression using anti-DCP antibody and anti-NX-DCP antibody. DCP and NX-DCP expression scores were calculated by multiplying staining intensity grade by percentage of stained area. Serum DCP and NX-DCP levels were determined in 89 patients. We evaluated the relationship between tumor expression, serum level, and pathomorphological findings. RESULTS: Intrahepatic metastasis (im) was significantly more frequent in cases with high DCP expression than in cases with low DCP expression. High NX-DCP expression was associated with significantly lower histological grade, and less frequent im or portal vein invasion (vp) than low NX-DCP expression. Serum DCP was correlated with DCP expression, but serum NX-DCP was not correlated with NX-DCP expression. DCP-positive (≥40 mAU/L), NX-DCP-positive (≥90 mAU/L), and DCP/NX-DCP ratio-positive (≥1.5) cases were associated with significantly larger tumor size and more frequent vp than negative cases. DCP was rarely expressed, but NX-DCP was frequently expressed in non-cancerous liver tissues. Patients with NX-DCP expression-negative tumors showed a lower survival rate than those with NX-DCP expression-positive tumors (p = 0.04), whereas the survival in serum NX-DCP-positive cases was lower than that of serum negative cases (p = 0.02). CONCLUSIONS: DCP and NX-DCP were produced in HCC tissues, but differed in expression level and biological properties. DCP expression, serum DCP or NX-DCP level, and DCP/NX-DCP ratio were closely related to malignant properties of HCC.

[A Case of Pancreatic Head Cancer Showing Pathological Complete Response to Neoadjuvant Chemoradiation Therapy].

The patient was a 64-year-old woman. She was referred to our institute because of a chief complaint of upper abdominal pain. Abdominal computed tomographic scan revealed a 35 mm hypovascular tumor in the pancreatic head and superior mesenteric vein (SMV), as well as thrombosis. We chose neoadjuvant chemoradiation therapy (NACRT) (S-1/RT, 50.4 Gy/28 Fr) and anticoagulants. After the treatment, the primary lesion showed a partial response, and the SMV thrombosis was reduced. We performed pancreaticoduodenectomy. Histopathological examination revealed no cancer cells in the pancreas. Pathological evaluation revealed grade Ⅳ tumor according to the Evans classification. The patient had had no recurrence for 10 months after the pancreaticoduodenectomy.

Evaluation of immunohistochemistry using two different antibodies and procedures for primary lung adenocarcinoma harboring anaplastic lymphoma kinase rearrangement.

Rearrangements of anaplastic lymphoma kinase (ALK) have been recently identified in non-small cell lung carcinomas. Previous studies have revealed characteristic features, including adenocarcinoma histology and mucin production, in ALK-positive lung carcinoma. The present study evaluated immunohistochemistry (IHC) in ALK-positive lung carcinoma using two different antibodies, clone 5A4 and D5F3, and compared the results. On the basis of the aforementioned characteristic features, out of 359 primary lung carcinomas, the ALK status of 14 adenocarcinomas was screened using the intercalated antibody-enhanced polymer (iAEP) method with antibody 5A4, and this was compared with the ALK status obtained using rabbit monoclonal antibody D5F3 and fluorescence in situ hybridization for ALK. Eight cases were demonstrated to be ALK-positive by IHC. Seven cases exhibited ALK rearrangement, which was demonstrated by fluorescence in situ hybridization. The IHC for ALK obtained using D5F3 was comparable with that of the iAEP and exhibited low heterogeneity. This finding suggests that IHC for ALK could be useful in limited tissue samples, such as biopsy specimens or cytology, for the screening of ALK-positive lung carcinoma. In the present study, it was demonstrated that IHC with ALK monoclonal antibody D5F3 was useful for screening lung adenocarcinoma harboring ALK rearrangement.

Evaluation of endoscopic cytological diagnosis of unresectable pancreatic cancer prior to and after the introduction of endoscopic ultrasound-guided fine-needle aspiration.

With the advances in the multidisciplinary treatment of pancreatic cancer (PC) over the last few years, it is crucial to obtain a histopathological diagnosis prior to treatment. Histopathological diagnosis for unresectable PC is currently performed with endoscopic retrograde cholangiopancreatography (ERCP) in combination with endoscopic ultrasound-guided fine-needle aspiration (EUS-FNA). We retrospectively assessed the results of these two methods and investigated diagnostic performance according to the location of the lesion and the complications. This study was conducted on a series of 263 consecutive cases of unresectable PC diagnosed with endoscopic cytology. Up to 2006, ERCP-guided cytology (group A) was performed as the first choice for the diagnosis of PC. EUS-FNA was introduced in 2007 and became the first choice thereafter (group B), except in cases with obstructive jaundice, in which ERCP-guided cytology during endoscopic biliary stenting (EBS) remains the first choice. There were statistically significant differences in the overall cancer-positive rate between groups A and B (60.4 vs. 75.3%, P=0.01). The cancer-positive rate in the pancreatic body and tail was significantly higher in group B (59.5 vs. 83.3%, P=0.005), whereas there were no significant differences regarding cancer of the pancreatic head. The complication rate was 4.95% in group A and 3.09% in group B (P=0.448). The endoscopic cytology cancer-positive rate in unresectable PC cases was increased as a result of the introduction of EUS-FNA. In conclusion, we recommend performing EUS-FNA in combination with ERCP-guided cytology in cases with a lesion in the pancreatic head that requires EBS.

Evaluation of endoscopic transpapillary brushing cytology for the diagnosis of bile duct cancer based on the histopathologic findings.

BACKGROUND AND AIM: Diagnosis of the bile duct cancer still needs more accuracy. Studies on endoscopic retrograde cholangiopancreatography (ERCP)-guided brushing cytology were carried to evaluate the role of the endoscopic transpapillary brushing cytology for the diagnosis of bile duct cancer. PATIENTS AND METHOD: The study involved 76 consecutive patients who underwent ERCP-guided bile duct cytology for the diagnosis of bile duct cancer from 2008 to August 2012. Three types of cytological specimens were obtained using different sampling methods, i.e., bile aspiration cytology (BAC), brush tip cytology (BTC), and post brushing bile cytology (PBC), to investigate their diagnostic abilities, and comparatively studied with each macroscopic type of the surgically resected specimens. RESULTS: The cancer-positive rate was 67.1 % (BAC alone: 41.9 %), and the use of BTC and PBC in addition to BAC yielded a statistically significant increase of the cancer-positive rate (p = 0.0031). In 34 resected cases, the cancer-positive rate in relation to the macroscopic type was improved by the addition of BTC and PBC to BAC alone for the papillary (87.5 vs. 40.0 %, p = 0.071) and nodular (100 vs. 70.0 %, p = 0.0603) types, but not for the flat type (62.5 vs. 57.1 %; p = 0.7651). CONCLUSION: The diagnostic ability of ERCP-guided brushing cytology could be improved by the addition of PBC. However, the cancer-positive rate was the lowest for the flat type of bile duct cancer.

Pegylated interferon-α2a inhibits proliferation of human liver cancer cells in vitro and in vivo.

PURPOSE: We investigated the effects of pegylated interferon-α2a (PEG-IFN-α2a) on the growth of human liver cancer cells. METHODS: The effect of PEG-IFN-α2a on the proliferation of 13 liver cancer cell lines was investigated in vitro. Cells were cultured with medium containing 0-4,194 ng/mL of PEG-IFN-α2a, and after 1, 2, 3, or 4 days of culture, morphologic observation and growth assay were performed. After hepatocellular carcinoma (HCC) cells (HAK-1B and KIM-1) were transplanted into nude mice, various doses of PEG-IFN-α2a were subcutaneously administered to the mice once a week for 2 weeks, and tumor volume, weight, and histology were examined. RESULTS: PEG-IFN-α2a inhibited the growth of 8 and 11 cell lines in a time- and dose-dependent manner, respectively, although the 50% growth inhibitory concentrations of 7 measurable cell lines on Day 4 were relatively high and ranged from 253 ng/mL to 4,431 ng/mL. Various levels of apoptosis induction were confirmed in 8 cell lines. PEG-IFN-α2a induced a dose-dependent decrease in tumor volume and weight, and a significant increase of apoptotic cells in the tumor. Subcutaneous administration of clinical dose for chronic hepatitis C (3 µg/kg, 0.06 µg/mouse) was effective and induced about 30-50% reduction in the tumor volume and weight as compared with the control. CONCLUSIONS: Although in vitro anti-proliferative effects of PEG-IFN-α2a were relatively weak, PEG-IFN-α2a induced strong anti-tumor effects on HCC cells in vivo. The data suggest potential clinical application of PEG-IFN-α2a for the prevention and treatment of HCC.

RECQL1 DNA repair helicase: a potential therapeutic target and a proliferative marker against ovarian cancer.

OBJECTIVE: This study analyzed the clinicopathological correlation between ovarian cancer (OC) and RECQL1 DNA helicase to assess its therapeutic potential. METHODS: Surgically resected OC from 118 retrospective cases, for which paraffin blocks and all clinical data were complete, were used in this study. RECQL1 and Ki-67 immunostaining were performed on sections to correlate RECQL1 staining with subtype and patient survival. Ten OC and two normal cell lines were then examined for RECQL1 expression and were treated with siRNA against RECQL1 to assess its effect on cell proliferation. RESULTS: Of the 118 cases of adenocarcinoma (50, serous; 26, endometrioid; 21, clear cell; 15, mucinous; 6, other histology), 104 (90%) showed varying levels of RECQL1 expression in the nuclei of OC cells. The Cox hazards model confirmed that diffuse and strong staining of RECQL1 was correlated with histological type. However, RECQL1 expression did not correlate with overall patient survival or FIGO stage. In vitro, RECQL1 expression was exceptionally high in rapidly growing OC cell lines, as compared with normal cells. Using a time-course analysis of RECQL1-siRNA transfection, we observed a significant inhibition in cell proliferation. CONCLUSIONS: RECQL1 DNA helicase is a marker of highly proliferative cells. RECQL1-siRNA may offer a new therapeutic strategy against various subtypes of OC, including platinum-resistant cancers, or in recurrent cancers that gain platinum resistance.

Evaluation of magnifying endoscopy using narrow band imaging using ex vivo bile duct (with video).

BACKGROUND AND AIM: Detailed endoscopic findings of the bile duct mucosa, even of the non-neoplastic mucosa, have not yet been established. The aim of the present study was to compare a currently used video cholangioscope (CCS) with a magnifying endoscope (ME) that is commonly used for the gastrointestinal tract, for visualization of the bile duct mucosa. METHODS: Ten freshly resected common bile ducts were used in this study. We observed the non-neoplastic bile duct mucosa with CCS and ME, and carried out both conventional white light imaging and narrow band imaging. After histological diagnosis, the 10 specimens were classified into three categories according to the degree of histological inflammation: normal to mild, moderate, and severe. Then, we examined the relationship between the magnifying endoscopic findings and the histopathological findings. RESULTS: In eight of the 10 cases, the visualization obtained with CCS was inferior to that obtained by ME. Five specimens were classified as normal to mild inflammation, and many oval-shaped, depressed areas and a fine, regular network of the microvessels were observed by ME on the mucosal surfaces of these specimens. The remaining specimens were classified as moderate or severe inflammation, and the aforementioned findings could not be clearly visualized. CONCLUSION: CCS does not allow visualization of the bile duct mucosa with high sensitivity. Oval-shaped depressed areas and a fine, regular network of microvessels are characteristic endoscopic features of non-neoplastic bile duct mucosa without inflammation.

A case of acute pancreatitis following endoscopic biopsy of the ampulla of Vater.

Ampullary tumors are diagnosed by endoscopic biopsy of the ampulla of Vater. We encountered a rare case of acute pancreatitis following endoscopic biopsy of the ampulla. A 53-year-old man referred to our hospital for detailed examination of a suspected tumor of the ampulla of Vater. We conducted endoscopic biopsy from the ampulla. He developed severe abdominal pain four hours after the procedure. The serum amylase and serum lipase were elevated and abdominal computed tomography (CT) revealed pancreatic enlargement and diffuse stranding of the peri-pancreatic fat, compatible with the findings of acute pancreatitis. We diagnosed the patient as having acute pancreatitis caused by endoscopic biopsy of the ampulla of Vater. Conservative therapy improved his condition, however, a large pancreatic walled-off necrosis (WON) developed. Therefore, we performed endoscopic ultrasonography (EUS)-guided cyst drainage on the 74th day after admission. The WON diminished gradually in size and the symptoms disappeared, and the patient was discharged in good physical condition on the 137th day after admission. In this case, the ampullary biopsy may have caused mucosal edema or intraductal hematoma, resulting in pancreatic duct obstruction. It is important for endoscopists both to be aware of this potential complication following endoscopic biopsy of the ampulla and to inform the patients about possible complications of this procedure.

Intraductal neoplasm of the intrahepatic bile duct: clinicopathological study of 24 cases.

AIM: To investigate the clinicopathological features of intraductal neoplasm of the intrahepatic bile duct (INihB). METHODS: Clinicopathological features of 24 cases of INihB, which were previously diagnosed as biliary papillomatosis or intraductal growth of intrahepatic biliary neoplasm, were reviewed. Mucin immunohistochemistry was performed for mucin (MUC)1, MUC2, MUC5AC and MUC6. Ki-67, P53 and ß-catenin immunoreactivity were also examined. We categorized each tumor as adenoma (low grade), borderline (intermediate grade), and malignant (carcinoma in situ, high grade including tumors with microinvasion). RESULTS: Among 24 cases of INihB, we identified 24 tumors. Twenty of 24 tumors (83%) were composed of a papillary structure; the same feature observed in intraductal papillary neoplasm of the bile duct (IPNB). In contrast, the remaining four tumors (17%) showed both tubular and papillary structures. In three of the four tumors (75%), macroscopic mucin secretion was limited but microscopic intracellular mucin was evident. Histologically, 16 tumors (67%) were malignant, three (12%) were borderline, and five (21%) were adenoma. Microinvasion was found in four cases (17%). Immunohistochemical analysis revealed that MUC1 was not expressed in the borderline/adenoma group but was expressed only in malignant lesions (P = 0.0095). Ki-67 labeling index (LI) was significantly higher in the malignant group than in the borderline/adenoma group (22.2 ± 15.5 vs 7.5 ± 6.3, P < 0.01). In the 16 malignant cases, expression of MUC5AC showed borderline significant association with high Ki-67 LI (P = 0.0622). Nuclear expression of ß-catenin was observed in two (8%) of the 24 tumors, and these two tumors also showed MUC1 expression. P53 was negative in all tumors. CONCLUSION: Some cases of INihB have a tubular structure, and are subcategorized as IPNB with tubular structure. MUC1 expression in INihB correlates positively with degree of malignancy.