van der Waals Decoration of Ultra-High-Q Silica Microcavities for χ(2)-χ(3) Hybrid Nonlinear Photonics.

Optical nonlinear processes are indispensable in a wide range of applications, including ultrafast lasers, microscopy, and quantum information technologies. Among the diverse nonlinear processes, second-order effects usually overwhelm the higher-order ones, except in centrosymmetric systems, where the second-order susceptibility vanishes to allow the use of the third-order nonlinearity. Here we demonstrate a hybrid photonic platform whereby the balance between second- and third-order susceptibilities can be tuned flexibly. By decorating ultra-high-Q silica microcavities with atomically thin tungsten diselenide, we observe cavity-enhanced second-harmonic generation and sum-frequency generation with continuous-wave excitation at a power level of only a few hundred microwatts. We show that the coexistence of second- and third-order nonlinearities in a single device can be achieved by carefully choosing the size and location of the two-dimensional material. Our approach can be generalized to other types of cavities, unlocking the potential of hybrid systems with controlled nonlinear susceptibilities for novel applications.

Optical coupling of individual air-suspended carbon nanotubes to silicon microcavities.

Carbon nanotubes are a telecom band emitter compatible with silicon photonics, and when coupled to microcavities, they present opportunities for exploiting quantum electrodynamical effects. Microdisk resonators demonstrate the feasibility of integration into the silicon platform. Efficient coupling is achieved using photonic crystal air-mode nanobeam cavities. The molecular screening effect on nanotube emission allows for spectral tuning of the coupling. The Purcell effect of the coupled cavity-exciton system reveals near-unity radiative quantum efficiencies of the excitons in carbon nanotubes.

Super-resolution fluorescence imaging of carbon nanotubes using a nonlinear excitonic process.

Highly efficient exciton-exciton annihilation process unique to one-dimensional systems is utilized for super-resolution imaging of air-suspended carbon nanotubes. Through the comparison of fluorescence signals in linear and sublinear regimes at different excitation powers, we extract the efficiency of the annihilation processes using conventional confocal microscopy. Spatial images of the annihilation rate of the excitons have resolution beyond the diffraction limit. We investigate excitation power dependence of the annihilation processes by experiment and Monte Carlo simulation, and the resolution improvement of the annihilation images can be quantitatively explained by the superlinearity of the annihilation process. We have also developed another method in which the cubic dependence of the annihilation rate on exciton density is utilized to achieve further sharpening of single nanotube images.

Enhanced Single-Photon Emission from Carbon-Nanotube Dopant States Coupled to Silicon Microcavities.

Single-walled carbon nanotubes are a promising material as quantum light sources at room temperature and as nanoscale light sources for integrated photonic circuits on silicon. Here, we show that the integration of dopant states in carbon nanotubes and silicon microcavities can provide bright and high-purity single-photon emitters on a silicon photonics platform at room temperature. We perform photoluminescence spectroscopy and observe the enhancement of emission from the dopant states by a factor of ∼50, and cavity-enhanced radiative decay is confirmed using time-resolved measurements, in which a ∼30% decrease of emission lifetime is observed. The statistics of photons emitted from the cavity-coupled dopant states are investigated by photon-correlation measurements, and high-purity single photon generation is observed. The excitation power dependence of photon emission statistics shows that the degree of photon antibunching can be kept high even when the excitation power increases, while the single-photon emission rate can be increased to ∼1.7 × 107 Hz.

The prognostic impact of differentiation at the invasive front of biliary tract cancer.

BACKGROUND: The invasive front of tumor can provide prognostic information in many cancers. We investigated the prognostic morphological factors at the invasive front including tumor differentiation (Difinv ) and tumor budding (Bud) in biliary tract cancer (BTC). METHODS: The resected specimen from the 299 BTC patients were examined. Intrahepatic cholangiocarcinoma, extrahepatic cholangiocarcinoma, gallbladder cancer, and ampulla of Vater cancer were found in 16%, 48%, 17%, and 19%, respectively. Difinv grade (G) 3 and Bud foci ≥5 were found in 47% and 10%. Tumor with Difinv G3 showed the high frequencies of Bud, vascular invasion (Ve) and nodal metastasis (LN) compared to tumor with Difinv G1/2 (Bud: 21% vs 0%, Ve: 71% vs 50%, LN: 52% vs 36%). Multivariate analysis revealed that the independent predictors were Difinv G3 (HR: 1.71), Bud foci ≥5 (HR: 2.14), Ve (HR: 1.56) and LN (HR: 2.59) in overall survival and were positive resection margin (HR: 1.71), Difinv G3 (HR: 1.75), Ve (HR: 1.50), and LN (HR: 2.19) in relapse free survival. CONCLUSION: Poor differentiation at the invasive front of tumor was associated with poor prognosis and early relapse in BTC patients.

[Resection of an Advanced Rectal Gastrointestinal Stromal Tumor Following Neoadjuvant Chemotherapy].

A 66-year-old man was referred to our hospital after being diagnosed with a pelvic tumor. A subsequent transperineal biopsy revealed spindle cells with CD34·c-kit(+). An enhanced computed tomography scan showed a giant rectal-derived tumor in the pelvis. The tumor was pressing on the urinary bladder and the prostate, and appeared to invade the posterior wall ofthese organs. The patient was diagnosed with rectal GIST, and neoadjuvant therapy with 400mg/day imatinib was initiated. Three months later, the tumor reduction rate was at 33.6%, and surgery was performed. The operative method applied was pelvic exenteration and ileal conduit, for local R0 resection. The patient has remained recurrence free for 2.5 years since the surgery.

Comparison of postoperative early and late complications between pancreas-sparing duodenectomy and pancreatoduodenectomy.

PURPOSE: Pancreas-sparing duodenectomy (PSD) represents an alternative procedure to pancreatoduodenectomy (PD) for patients with duodenal neoplasms. METHODS: The postoperative early and late complications of 21 patients who underwent PSD between 1992 and 2014 were compared with those of 44 patients with soft pancreatic parenchyma who underwent PD between 2009 and 2014. RESULTS: The median operation time and blood loss were less in the PSD group than in the PD group (P < 0.001). The overall incidence of early complications was less in the PSD group than in the PD group (PSD with ampullectomy vs. PSD without ampullectomy vs. PD; 45.5 vs. 20.0 vs. 56.8 %). The incidence of pancreatic fistula formation and overall incidence of late complications were also less in the PSD group than in the PD group (P = 0.031, 0.020). There were no complications related to the pancreatic endocrine or exocrine functions in the PSD group. CONCLUSION: PSD is a less-invasive procedure and has the advantage over PD of preserving the pancreas.

Measure of pancreas transection and postoperative pancreatic fistula.

BACKGROUND: In pancreaticoduodenectomy (PD), a standard protocol for pancreas transection has not been established although the method of pancreas transection might be involved in the occurrence of postoperative pancreatic fistula (POPF). This study aimed to compare whether pancreas transection by ultrasonically activated shears (UAS) or that by scalpel contributed more to POPF development. METHODS: A prospective database of 171 patients who underwent PD for periampullary tumor at National Cancer Center Hospital East between January 2010 and June 2013 was reviewed. Among the 171 patients, 93 patients with soft pancreas were specifically included in this study. Surgical results and background were compared between patients with pancreas transection by UAS and scalpel to evaluate the effectiveness of UAS on reducing POPF. RESULTS: Body mass index, main pancreatic duct diameter, or other clinicopathologic factors that have been reported as predictive factors for POPF were not significantly different between the two groups. The incidence of all grades of POPF and that of grade B were significantly lower in the scalpel group (52%, 4%) than in the UAS group (74%, 42%). Postoperative complications ≥ grade III were also significantly fewer in the scalpel group. CONCLUSIONS: Scalpel transection was less associated with POPF than UAS transection in patients who underwent PD for soft pancreas. The method of pancreas transection plays an important role in the prevention of clinical POPF.

Risk factors for malignancy in branched-type intraductal papillary mucinous neoplasms of the pancreas during the follow-up period.

BACKGROUND: The international consensus guidelines for the management of intraductal papillary mucinous neoplasm (IPMN) of the pancreas were revised in 2012 Tanaka (Pancreatology 12(3):183-197, 2012), making the indications for operation less aggressive. Therefore, the number of branch duct-type IPMN (BD-IPMN) patients requiring follow-up care is expected to increase in the future. METHODS: The aim of this study was to identify risk factors for malignancy in BD-IPMN patients during the follow-up period. This study included 47 BD-IPMN patients without a mural nodule (MN) at the time of initial diagnosis and who subsequently underwent resection after a follow-up period of more than 3 months. Data for the patients were reviewed retrospectively, and the clinicopathological factors were investigated. RESULTS: In a univariate analysis, age (≧ 65 years), an increase in the main pancreatic duct (MPD) diameter, the MPD diameter at resection (≧ 5 mm), and the occurrence of MN were significantly associated with malignancy. The occurrence of MN was the only significant factor in a multivariate analysis. In addition, 7 of the 17 patients (41.2 %) who only exhibited an increase in the cyst diameter during the follow-up period were diagnosed as having malignancies. All 6 patients who exhibited an increase in the cyst diameter of 100 % or more were diagnosed as having carcinoma. CONCLUSIONS: During the follow-up period, the incidence of malignancy was higher among patients with BD-IPMNs and the occurrence of MN, an increase in the MPD diameter, or an increase ratio of 100 % or more in cyst diameter than the others; resection was recommended for these patients.

Limited subtotal gastrectomy for early remnant gastric cancer.

BACKGROUND: Detection of early remnant gastric cancer (ERGC) is increasing as a result of the development of endoscopic technology and a surveillance program. The aim of this study was to evaluate the results of limited subtotal gastrectomy (SG) surgery for ERGC compared to total gastrectomy (TG). METHODS: We retrospectively reviewed a database of 72 consecutive patients with remnant gastric cancer who underwent laparotomy at the National Cancer Center Hospital East between January 1993 and December 2008. Thirty-five patients with a preoperative diagnosis of ERGC underwent curative resection: 13 SG and 22 conventional TG. Patients and tumor characteristics, operative results, and postoperative assessments 1 year after surgery were compared between the two groups. RESULTS: Operating time, blood transfusion, and hospital stay were similar in the two groups. In the SG group, blood loss and postoperative recovery of body weight tended to be better than in the TG group. There was no dumping syndrome in the SG group, while this occurred in three patients in the TG group. The levels of hemoglobin and total protein were higher 1 year after remnant gastrectomy in the SG group than in the TG group. No recurrence of gastric cancer was detected in the SG group during median follow-up of 99.2 months. CONCLUSION: In comparison to TG, limited SG surgery for ERGC improved the postoperative course, with no recurrence of cancer. Therefore, SG is a safe and effective treatment for ERGC.

Surgical procedure depending on the depth of tumor invasion in duodenal cancer.

BACKGROUND: Duodenal cancer excluding Vater's papilla cancer is a relatively rare disease entity; therefore, the most appropriate operative methods depending on the tumor condition, such as the tumor site and/or depth of invasion, still remain unclear. The aim of this study is to determine an appropriate operative method and an appropriate extent of lymph node dissection depending on tumor site or tumor invasion depth. METHODS: Data of a total of 35 patients with duodenal cancer who underwent resectional surgery with curative intent were reviewed retrospectively, and the clinicopathological factors and survival outcomes were investigated. RESULTS: Overall 5-year survival rates of all resected cases were 63.0% (median survival: 9.1 years). Multivariate analysis identified histological G3/4 (P = 0.002) and presence of lymph node metastasis (P = 0.004) as independent adverse prognostic factors. Of the 35 patients, 11 (31.4%) had lymph node metastasis. In all patients with the tumor invasion depth within limited to the mucosa or submucosa (T1a or T1b), lymph node metastasis was absent (0/15 patients). T2/3/4 tumor (P < 0.001) and G3/4 (P = 0.021) were identified as predictors of the presence of lymph node metastasis. Four (11.4%) of the 35 patients had metastasis in the infrapyloric node. CONCLUSIONS: Limited resection is sufficient for patients with T1a tumor. In the case of T1b tumor, limited resection or pancreatoduodenectomy may be selected after performing pancreaticoduodenal node biopsy as sentinel lymph node biopsy. For patients with T2-4 tumor, pancreatoduodenectomy or substomach preserving pancreatoduodenectomy (excepting Pylorus-preserving pancreatoduodenectomy) with regional lymph node dissection should be performed.

Laparoscopic proximal gastrectomy with jejunal interposition for gastric cancer in the proximal third of the stomach: a retrospective comparison with open surgery.

BACKGROUND: The incidence of cancer in the proximal third of the stomach is increasing. Laparoscopic proximal gastrectomy (LPG) seems an attractive option for the treatment of early-stage proximal gastric cancer but has not gained wide acceptance because of technical difficulties, including the prevention of severe reflux. In this study, we describe our technique for LPG with jejunal interposition (LPG-IP) and evaluate its safety and feasibility. METHODS: In this retrospective analysis, we reviewed the data of patients with proximal gastric cancer who underwent LPG-IP (n = 22) or the same procedure with open surgery (OPG-IP; n = 68) between January 2008 and September 2011. Short-term surgical variables and outcomes were compared between the groups. The reconstruction method was the same in both groups, with creation of a 15 cm, single-loop, jejunal interposition for anastomosis. RESULTS: There were no differences in patient or tumor characteristics between the groups. Operation time was longer in the LGP-IP group (233 vs. 201 min, p = 0.0002) and estimated blood loss was significantly less (20 vs. 242 g, p < 0.0001). The average number of harvested lymph nodes did not differ between the two groups (17 vs. 20). There also were no differences in the incidence of leakage at the esophagojejunostomy anastomosis (9.1 vs. 7.4%) or other postoperative complications (27 vs. 32%). The number of times additional postoperative analgesia was required was significantly less in the LPG-IP group compared with the OPG-IP group (2 vs. 4, p < 0.0001). CONCLUSIONS: LPG-IP has equivalent safety and curability compared with OPG-IP. Our results imply that LPG-IP may lead to faster recovery, better cosmesis, and improved quality of life in the short-term compared with OPG-IP. Because of the limitations of retrospective analysis, a further study should be conducted to obtain definitive conclusions.

Short-term outcome of total laparoscopic distal gastrectomy for overweight and obese patients with gastric cancer.

BACKGROUND: Laparoscopic distal gastrectomy for gastric cancer has been firmly established in recent decades but still is a difficult procedure, especially for obese patients, as with open surgery. This study aimed to evaluate the perioperative outcome of total laparoscopic distal gastrectomy (TLDG) for early gastric cancer patients with a body mass index (BMI) exceeding 25 kg/m(2) and to consider countermeasures to this. METHODS: Perioperative outcomes were compared between 42 patients with a BMI exceeding 25 kg/m(2) [overweight or obese group (OWG)] and 174 patients with a BMI lower than 25 kg/m(2) [normal or underweight group (NWG)] who underwent TLDG between September 2010 and December 2012. RESULTS: The BMI was 26.0 ± 1.4 kg/m(2) in the OWG group and 22.0 ± 2.1 kg/m(2) in the NWG group (P < 0.001). The groups did not differ in terms of age, sex, American Society of Anesthesiologists score, presence of diabetes, number of retrieved lymph nodes, number of metastatic lymph nodes, or metastatic lymph node ratio. The two groups did not differ significantly with respect to the extent of lymph node dissection [OWG: D1 (11.9 %), D1+ (66.7 %), D2 (21.4 %) vs NWG: D1 (5.2 %), D1+ (51.7 %), D2 (43.1 %); P = 0.020] or tumor size (OWG: 25.5 ± 20.2 mm vs NWG: 33.0 ± 17.2 mm; P = 0.037). Differences in operation time (OWG: 212 ± 31 min vs NWG: 200 ± 35 min; P = 0.005) and estimated blood loss (OWG: 15 ± 22 ml vs NWG: 10 ± 34 ml; P = 0.013) seemed to have a minimal impact clinically. Postoperative complications including infectious complications and recovery after surgery did not differ between the two groups. CONCLUSIONS: For overweight and obese patients, TLDG was managed safely. The procedure was considered to be difficult but sufficiently feasible.

Infection control for prevention of pancreatic fistula after pancreaticoduodenectomy.

BACKGROUND/AIMS: Effectiveness of infection control for prevention of pancreatic fistula (PF) after pancreaticoduodenectomy (PD) is not clear. We analyzed the impact of infection on the development of PF and examined the effect of enhanced infection control to prevent PF. METHODOLOGY: Amylase level (D-amylase) and bacterial culture (D-culture) of drainage fluid were evaluated on POD 1, 3, 5 and 7, in 90 consecutive patients with soft pancreas who underwent PD. The study period was divided into two periods. The relationship between D-amylase and D-culture was examined, and the clinicopathological factors predicting PF were analyzed in the first period. Then, anti-infection measures were introduced in the second period, and the effect of enhanced infection control was examined. RESULTS: Twenty-nine out of 58 patients (50.0%) developed PF in the first period. D-amylase were higher in patients with D-culture infection than in those without it (p<0.05). D-amylase above 10,000IU/L on POD1 and D-culture infection on POD3 were independent predictive factors for PF by multivariate analysis (p<0.01). After introduction of enhanced infection control in the second period, four out of 32 patients (12.5%) developed PF. The rates of PF and D-culture infection were significantly reduced (p<0.05). CONCLUSIONS: Infection of drainage fluid is related to an increased level of amylase, resulting in PF. Enhanced infection control can effectively prevent PF after PD in soft pancreas.

Edaravone Administered Orally and Via Nasogastric Tube in Healthy Adults: A Comparative Bioavailability Phase 1 Study.

Intravenous edaravone is used to treat patients with amyotrophic lateral sclerosis. This randomized, open-label, two-way crossover, single-dose phase 1 study compared the relative bioavailability of a newly developed edaravone oral suspension when administered orally and via a nasogastric tube (NGT) as a model of percutaneous endoscopic gastrostomy tube administration in healthy adult subjects. Thirty-six subjects were randomly assigned to one of two groups, with 18 per group. Blood was collected pre- and post-dose for pharmacokinetic assessments; safety was evaluated. Plasma concentration-time profiles of unchanged edaravone were similar between administration routes. Comparative bioavailability analysis revealed that geometric least squares mean ratios (NGT/oral) for maximum plasma concentration and area under the plasma concentration-time curve from time zero to infinity of unchanged edaravone were 1.052 and 0.981, respectively. No serious adverse events or adverse drug reactions were reported. These results suggest that oral edaravone suspension can be administered directly to the stomach without dose adjustment via feeding tubes; both oral and NGT administration are well tolerated.

Impact of tumor-associated macrophages on invasive ductal carcinoma of the pancreas head.

Tumor-associated macrophages (TAMs) are candidate histological factors in invasive ductal carcinoma (IDC) of the pancreas. Tumor-associated macrophages can be affected by cancer-related inflammation and pancreatitis and interact with important invasive behavior in a recurrent manner in pancreatic IDC. These features may help elucidate the aggressiveness of pancreatic IDC. The aim of this study was to characterize TAMs in pancreatic IDC in comparison with chronic pancreatitis (CP) and to reveal TAM-related factors and the clinical impact of TAMs. CD68 (a pan-macrophage marker) and CD204 (an M2 macrophage marker) immunohistochemistry was carried out in pancreas head specimens from 107 IDC cases and 11 CP cases. Immunopositive cell areas were calculated at the periphery and center of the tumor. The distributions of macrophages in IDC and CP and the relationship between TAMs and histological tumor factors, survival, and recurrence were evaluated. Macrophages were more frequently observed in the lesion periphery than the center in IDC and CP. The density of macrophages was elevated in IDC compared to CP. Dense M2 macrophages at the tumor periphery were frequently seen in large tumors and showed an independent impact on overall survival and disease-free time. Early recurrence in the liver or the local manipulated area was associated with high accumulation of peripheral M2 macrophages. More M2 macrophages were seen in IDC than in CP in both the periphery and the center. High numbers of peripheral M2 macrophages were associated with large tumor size, early recurrence in the liver, local recurrence, and shortened survival time in patients with pancreatic IDC.

Clinicopathological features and prognostic factors of adenocarcinoma of the esophagogastric junction according to Siewert classification: experiences at a single institution in Japan.

BACKGROUND: Treatment strategy for adenocarcinoma of the esophagogastric junction (AEG) remains controversial. The aims of this study are to evaluate results of surgery for AEG, to clarify clinicopathological differences according to the Siewert classification, and to define prognostic factors. METHODS: We retrospectively analyzed 179 consecutive patients with Siewert type I, II, and III AEG who underwent curative (R0) resection at the National Cancer Center Hospital East between January 1993 and December 2008. RESULTS: Patients with AEG were divided according to tumor: 10 type I (5.6%), 107 type II (59.8%), and 62 type III (34.6%). Larger, deeper tumors and nodal metastasis were more common in type III than type II tumors. No significant differences were seen in 5-year survival rates among the three types: type I (51.4%), type II (51.8%), and type III (62.6%). Multivariate analysis showed that depth of tumor and mediastinal lymph node metastasis were independent prognostic indicators. The recurrence rate for patients with mediastinal lymph node metastasis was 87.5%. The risk factors for mediastinal lymph node metastasis were length of esophageal invasion and histopathological grade. CONCLUSIONS: Mediastinal lymph node metastasis and tumor depth were significant and independent factors for poor prognosis after R0 resection for AEG. Esophageal invasion and histopathological grade were significant and independent factors for mediastinal lymph node metastasis.

Clinicopathological features of stomach cancer with invasive micropapillary component.

BACKGROUND: Invasive micropapillary carcinoma has been recognized as a rare disease entity with aggressive tumor behavior. However, few reports have described invasive micropapillary carcinoma in the gastrointestinal tract, particularly its involvement in gastric cancer. METHODS: We retrospectively analyzed 930 patients diagnosed with gastric cancer who underwent gastrectomy, and we then histopathologically evaluated the existence of a regional invasive micropapillary component. Clinicopathological features were investigated in patients with an invasive micropapillary component and compared with such features in 100 patients with gastric adenocarcinoma, selected as stage-matched controls, who underwent gastrectomy during the same period. RESULTS: Of the 930 patients, 14 were histopathologically diagnosed with gastric cancer with a regional invasive micropapillary component. There were no significant differences in age, gender, tumor location, macroscopic type, or type of surgery between patients with an invasive micropapillary component and the pT-matched controls. Histopathologically, significant differences were observed in lymphatic infiltration, venous invasion, the percentage of cases with lymph node metastasis, and the median number of metastatic lymph nodes. The three-year disease-free and overall survival rates of patients with an invasive micropapillary component were 40.5 and 59.3%, respectively, compared with those for the stage-matched controls, which were 72.6 and 80.6%, respectively (p = 0.02 and 0.07). CONCLUSIONS: Patients with gastric cancer with a regional invasive micropapillary component showed marked cancer infiltration in the lymphatic pathway and poor prognosis after gastrectomy.

Surgical outcome of liver transection by the crush-clamping technique combined with Harmonic FOCUS™.

BACKGROUND: New energy devices are constantly being introduced for all types of surgery, including liver surgery. These devices help surgeons perform operations. Meanwhile, intraoperative blood loss is a concern of liver surgeons. Various methods to reduce intraoperative bleeding during liver resection have been reported. There are some reports that the use of energy devices was effective for liver transection. Recently, the Harmonic FOCUS™ (HF), an ultrasonically activated device, was developed. The shape of the HF is similar to that of Kelly forceps. Hepatectomy can be performed by the clamp-crushing method using the HF instead of Kelly forceps. We obtained good results of liver resection with the HF, and report these outcomes in this study. METHODS: From November 2009 to March 2011, a total of 51 patients underwent hepatectomy with the use of the HF. The control group consisted of 59 patients who underwent hepatectomy without the HF from February 2009 to September 2009. The surgical outcomes were evaluated and compared retrospectively. RESULTS: Mean blood loss was 640 mL in the HF group compared to 1,176 mL in the control group. The number of patients needing a blood transfusion was smaller in the HF group (p = 0.02). Mean operative time was shorter in the HF group (171 vs. 235 min, p < 0.001). All these surgical outcomes were significantly better in the HF group. Postoperative morbidity was not increased in the HF group, and we could perform liver transection safely. CONCLUSION: The crush-clamping method combined with the HF is effective for liver transection. Liver resection can be performed quickly using this method.

Intraductal oncocytic papillary neoplasm of the extrahepatic bile duct: report of a case.

We report a rare case of an intraductal oncocytic papillary neoplasm (IOPN) of the extrahepatic bile duct. A 66-year-old man was admitted to our hospital for investigation of right-sided back pain. Ultrasonography, computed tomography and magnetic resonance imaging showed a papillary lesion, 3 cm in diameter, in the middle bile duct, invaginating into the cystic duct. We made a provisional diagnosis of middle bile duct cancer and performed substomach-preserving pancreatoduodenectomy. Macroscopically, the middle bile duct contained a two-humped papillary tumor, one tip of which invaginated into the cystic duct. Microscopically, the tumor consisted of cuboidal cells with abundant eosinophilic cytoplasm resembling that of oncocytes and a fine fibrovascular core. The tumor cells were stained strongly with antimitochondria antibody. Based on these findings, the tumor was diagnosed histologically as IOPN of the extrahepatic bile duct. The patient died of prostate cancer 51 months after surgery, but without evidence of recurrence of the IOPN.