Impact of a new dedicated sheath device for tissue sampling of biliary stricture on pathological diagnostic yield: Retrospective study.

Background and study aims Endoscopic transpapillary biliary forceps biopsy (TBFB) is a common method for obtaining specimens from biliary lesions. Its diagnostic yield is unsatisfactory; to overcome this disadvantage, a dedicated sheath has been developed. This study aimed to evaluate the outcomes of conventional TBFB and TBFB with a novel sheath device. Patients and methods Consecutive patients who underwent TBFB between January 2020 and December 2021 were retrospectively evaluated. The rate of obtaining adequate samples, failed attempts at forceps insertion into the bile duct, and sensitivity were compared between the two groups. Results Ninety-two patients who underwent 115 endoscopic retrograde cholangiopancreatographies (76 in the conventional group vs. 39 in the dedicated sheath group) were included. The rates of obtaining adequate samples, failed attempts of the forceps into the bile duct, and sensitivity were 72.4% vs. 89.7% ( P = 0.03), 28.3% vs. 0% ( P < 0.01), and 66.7% vs. 88.9% ( P = 0.02), respectively. Conclusions TBFB with the novel sheath device contributed to improved sensitivity for diagnosis of biliary stricture without insertion of forceps outside the bile duct.

Efficacy of lymph node dissection for duodenal cancer according to the lymph node station.

Background: Lymph node metastasis (LNM) is associated with poor prognosis in patients with duodenal cancer (DC). However, the efficacy and optimal extent of lymph node (LN) dissection have not been thoroughly discussed. Methods: A total of 98 consecutive patients with DC who underwent surgical resection (pancreatoduodenectomy, n = 55; partial resection, n = 32; pancreas-sparing total duodenectomy, n = 9) were retrospectively analyzed. The LN stations located upstream of the lymphatic flow were defined as Np stations according to tumor location, whereas the others were defined as Nd stations. The association between the dissection of each LN station and survival outcome was investigated using the efficacy index (EI; percentage of metastases to lymph nodes in each station multiplied by the 5-year survival rate of metastatic cases). Results: The survival of patients with LNM at the Nd stations (n = 6) was significantly worse than that of patients with LNM only at the Np stations (n = 20) (relapse-free survival, median survival time [MST], 6.0 vs. 48.4 months, p < 0.001; overall survival, MST, 15.1 vs. 96.0 months, p < 0.001). Multivariate analysis identified LNM at Nd stations as an independent prognostic factor for overall survival (hazard ratio 9.92; p = 0.015). The Np stations had a high EI (range, 8.34-20.88), whereas the Nd stations had an EI of 0, regardless of the tumor location. Conclusions: LN dissection of the Np stations contributed to acceptable survival, whereas LNM of the Nd stations led to poor survival, possibly reflecting advanced tumor progression to systemic disease in patients with DC.

Prognostic impact of the distance from the root of splenic artery to tumor in the patients with pancreatic body or tail cancer.

BACKGROUND: The impact of the distance from the root of splenic artery to tumor (DST) on the prognosis and optimal surgical procedures in the patients with pancreatic body/tail cancer has been unclear. METHODS: We retrospectively analyzed 94 patients who underwent distal pancreatectomy (DP) and 17 patients who underwent DP with celiac axis resection (DP-CAR) between 2008 and 2018. RESULTS: The 111 patients were assigned by DST length (in mm) as DST = 0: n = 14, 0

Discordant microsatellite instability findings in two samples from a patient with biliary cancer that responded to pembrolizumab.

Microsatellite instability (MSI) is a key marker to predict response to immune checkpoint inhibitors; however, only 1-2% of biliary cancers have this genomic feature. In a patient with hilar biliary cancer, MSI was examined in two cancer specimens (forceps biopsy from the biliary stricture and endoscopic ultrasound-guided fine-needle aspiration biopsy [EUS-FNAB] from the adjacent lymph node). We observed discordant results, as high frequency of MSI was found only in the forceps biopsy. Although the FNAB sample was 10 times larger than that of the forceps biopsy, the tumor concentration was much lower, which is a possible reason for the discordance. Besides, immunohistochemistry of four mismatch-repair (MMR) proteins showed proficient MMR expressions. The tumor became refractory to gemcitabine, cisplatin, and S-1 but responded well to pembrolizumab. Caution is needed for sample selection and for interpretation of the test's results, to avoid missing rare chance for effective molecular target agents.

Optimization of endoscopic ultrasound-guided tissue sample acquisition for commercially available comprehensive genome profiling.

BACKGROUND AND AIM: Optimal tumor samples are crucial for successful analysis using commercially available comprehensive genomic profiling (CACGP). However, samples acquired by endoscopic ultrasound-guided tissue acquisition (EUS-TA) are occasionally insufficient, and no consensus on the optimal number of needle passes required for CACGP exists. This study aimed to explore the optimal number of needle passes required for EUS-TA to procure an ideal sample fulfilling the prerequisite criteria of CACGPs. METHODS: Patients who underwent EUS-TA for solid masses between November 2019 and July 2021 were retrospectively studied. The correlation between the acquisition rate of an ideal sample and the number of needle passes mounted on a microscope slide was evaluated. Additionally, the factors predicting a successful analysis were investigated in patients scheduled for CACGP using EUS-TA-obtained samples during the same period. RESULTS: EUS-TAs using 22- and 19-gauge (G) needles were performed in 336 and 57 patients, respectively. There was a positive correlation between the acquisition rate and the number of passes using a 22-G needle (38.9%, 45.0%, 83.7%, and 100% for 1, 2, 3, and 4 passes, respectively), while no correlation was found with a 19-G needle (84.2%, 83.3%, and 85.0% for 1, 2, and 3 passes, respectively). The analysis success rate in patients with scheduled CACGP was significantly higher with ideal samples than with suboptimal samples (94.1% vs 55.0%, P < 0.01). CONCLUSIONS: The optimal estimated number of needle passes was 4 and 1-2 for 22- and 19-G needles, respectively.

Molecular genetic positioning of small intestine and papilla of Vater carcinomas including clinicopathological classification.

BACKGROUND: Small intestine carcinoma (SIC) cases in Japan have recently been treated with chemotherapy according to colorectal carcinoma classification, while papilla of Vater carcinoma (PVC) cases according to cholangiocarcinoma (CHC) classification. However, few research reports support the molecular genetic validity of these therapeutic choices. PATIENTS AND METHODS: Here, we investigated the clinicopathological and molecular genetic factors of SIC and PVC. We used the data from the Japanese version of The Cancer Genome Atlas. Additionally, molecular genetic data on gastric adenocarcinoma (GAD), colorectal adenocarcinoma (CRAD), pancreatic ductal adenocarcinoma (PDAC), and CHC were also referred to. RESULTS: This study consisted of tumor samples from 12 patients of SIC and three patients of PVC treated from January 2014 to March 2019. Among them, six patients had pancreatic invasion. t-Distributed stochastic neighbor embedding analysis showed that the gene expression pattern of SIC was similar not only to those of GAD and CRAD, but also to that of PDAC in the pancreatic invasion patients. In addition, PVC resembled the GAD, CRAD, and PDAC, rather than the CHC. The molecular genetic characteristics of the six patients with pancreatic invasion were: one had high microsatellite instability, two had a TP53 driver mutation, and three had tumor mutation burden values <1 mutation/Mb with no driver mutation. CONCLUSIONS: In this study, the extensive gene expression profiling of organ carcinomas newly suggests that SIC or PVC may resemble GAD, CRAD, and PDAC. In addition, the data demonstrate that pancreatic invasive patients may be classified into several subtypes using molecular genetic factors.

Discordance of microsatellite instability and mismatch repair immunochemistry occurs depending on the cancer type.

Microsatellite instability (MSI) and deficiency of mismatch repair (dMMR) are key markers for predicting the response of immune checkpoint inhibitors (ICIs) and screening for Lynch syndrome (LS). This study examined the incidences of and factors associated with the concordance of MSI and MMR in human cancers. A total of 518 formalin-fixed cancer tissues were analyzed for MSI and MMR immunohistochemistry (IHC). MSI was analyzed by a PCR-based method using Promega markers. Concordance with MMR expression and factors associated with concordance were analyzed. In 2 colorectal cancer samples, MMR IHC failed due to inadequate staining conditions. In the remaining 516 cancers, a high level of MSI (MSI-H) was identified in 113 cases, and dMMR was identified in 112. The concordance of MSI and MMR IHC was 98.3%. Only 9 cases (4 pancreatobiliary, 3 colorectal, and 2 endometrial cancers) were discordant. Of the 113 MSI-H cases, 4 (3.5%) were proficient MMR (pMMR); of the 403 microsatellite stability (MSS) cases, 5 (1.2%) were dMMR. The independent factors associated with MSI-H/dMMR included meeting Amsterdam II criteria, assay purpose, and sampling method. Multivariate analysis revealed that cancer type (gastrointestinal cancers or others) was associated with concordance of MSI and MMR IHC. Three LS cases with pancreatic or endometrial cancer demonstrated MSS and dMMR, and one biliary cancer showed MSI-H and pMMR. Discordance between MSI and MMR IHC occasionally occurs in pancreaticobiliary and endometrial cancers. When suspected, both MSI and MMR IHC should be done to judge the ICI indication and screen for LS.

Genetic medicine in companion diagnostics of germline BRCA testing of Japanese pancreatic cancer patients.

In 2021, Japan's national health insurance made germline BRCA (g.BRCA) testing available to unresectable pancreatic cancer (PC) patients as a companion diagnostic (CD) of the PARP inhibitor. This study investigated the incidence of the g.BRCA variant (g.BRCAv.) and the status of the genetic medicine associated with its testing. A total of 110 PC patients underwent the testing, five of whom (4.5%) had a deleterious g.BRCA2v. (all truncations) but no g.BRCA1v. The turnaround time (TAT) to the doctors was 13 days, and to the patients, 17 days. A higher incidence of a BRCA-related family history and a shorter TAT were seen in the g.BRCAv. patients, but they were insignificant (p = 0.085 and p = 0.059, respectively). Genetic counseling was not performed for three g.BRCA2v. patients because two of them had no accessible relatives and one died of the cancer before the genetic report was completed. Two families underwent generic counseling and testing based on the patient's genetic data. g.BRCAv. is recognized in a small fraction of PC cases, and the following genetic counseling is done more for the relatives than for the patients. TAT was constant and did not affect much on the genetic counseling, but the earlier testing is expected for patients with a deadly cancer.

Clinical implications of lymphadenectomy for invasive ductal carcinoma of the body or tail of the pancreas.

Aim: The appropriate extent of lymphadenectomy for pancreatic cancer of the body/tail has not been standardized worldwide. The present study evaluated the optimal extent of harvesting lymph nodes. Methods: Patients who underwent distal pancreatectomy for invasive ductal carcinoma of the pancreas between 2007 and 2018 were retrospectively reviewed. Patients were subclassified into three groups depending on the tumor location: pancreatic body (Pb), proximal pancreatic tail (Ptp), and distal pancreatic tail (Ptd). The pancreatic tail was further divided into even sections of Ptp and Ptd. Patterns of lymph node metastasis and the impact of lymph node metastasis on the prognosis were examined. Results: A total of 120 patients were evaluated. Fifty-eight patients had a tumor in the Pb, 38 in the Ptp, and 24 in the Ptd. No patients with a Ptd tumor had metastasis beyond the peripancreatic and splenic hilar lymph nodes (LN-PSH). All patients with metastasis to the lymph nodes along the common hepatic artery (LN-CHA) or along the left lateral superior mesenteric artery (LN-SMA) also had metastasis to the LN-PSH. Recurrence after surgery occurred significantly earlier in this population. In a multivariate analysis, metastasis to the LN-CHA or LN-SMA (hazard ratio [HR] 3.3; P = .04) was an independent risk factor for overall survival. Furthermore, high levels of preoperative serum CA19-9 (HR 10.9; P = .013) were a predictive factor for metastasis to the LN-CHA or LN-SMA. Conclusions: Metastasis to the LN-CHA or LN-SMA was rare but a significant prognostic factor in patients with pancreatic body/tail cancer.

Granular cell tumor of the pancreas with chronic dilation of the main pancreatic duct.

Although a granular cell tumor (GCT) can originate in various locations, GCT of the pancreas is a rare entity. We herein report a case of GCT of the pancreas with chronic dilation of the main pancreatic duct (MPD). The patient had been referred to our institution for epigastric pain 12 years ago at 50 years old. Multidetector-row computed tomography (MDCT) had shown dilation of the MPD up to 8 mm in diameter from the pancreatic body to the tail. However, she had refused additional workup and been lost to follow-up. She was referred to our institution at 62 years old, as dilation of the MPD had been noted again. Imaging studies showed that the MPD had become dilated up to 33 mm from the pancreatic body to the tail. MDCT showed a hypovascular nodule (6 mm in diameter) in the pancreatic neck, and the nodule was located at the origin of MPD dilation. Pancreatic cancer was considered as a possible differential diagnosis. Surgical treatment was planned for a therapeutic diagnosis, and distal pancreatectomy with splenectomy and lymphadenectomy was performed. The gross findings of the resected specimen revealed a pale-yellow solid tumor measuring 8 mm in diameter at the pancreatic neck. The histopathologic assessment revealed the tumor to be GCT of the pancreas. The characteristics of GCT of the pancreas, such as a tumor causing stenosis and dilation of the MPD frequently and being too small to detect on imaging studies, may lead to a misleading diagnosis of pancreatic cancer.

The Association Between Neoadjuvant Therapy and Pathological Outcomes in Pancreatic Cancer Patients After Resection: Prognostic Significance of Microscopic Venous Invasion.

BACKGROUND: The impact of neoadjuvant therapy (NAT) on pathological outcomes, including microscopic venous invasion (MVI), remains unclear in pancreatic cancer. METHODS: A total of 456 patients who underwent pancreatectomy for resectable and borderline resectable pancreatic cancer between July 2012 and February 2020 were retrospectively reviewed. Patients were divided into two groups: patients with NAT (n = 120, 26%) and those without NAT (n = 336, 74%). Clinicopathological factors, survival outcomes and recurrence patterns were analyzed. RESULTS: Regarding pathological findings, the proportion of MVI was significantly lower in patients with NAT than in those without NAT (43% vs 62%, P = 0.001). The 5-year survival rate in patients with NAT was significantly better than that in those without NAT (54% vs 45%, P = 0.030). A multivariate analysis showed that MVI was an independent prognostic factor for the overall survival (OS) (hazard ratio 2.86, P = 0.003) in patients who underwent NAT. MVI was an independent risk factor for liver recurrence (odds ratio [OR] 2.38, P = 0.016) and multiple-site recurrence (OR 1.92, P = 0.027) according to a multivariate analysis. The OS in patients with liver recurrence was significantly worse than that in patients with other recurrence patterns (vs lymph node, P = 0.047; vs local, P < 0.001; vs lung, P < 0.001). The absence of NAT was a significant risk factor for MVI (OR 1.93, P = 0.007). CONCLUSION: MVI was a crucial prognostic factor associated with liver and multiple-site recurrence in pancreatic cancer patients with NAT. MVI may be reduced by NAT, which may contribute to the improvement of survival in pancreatic cancer patients.

Microsatellite instability is biased in Amsterdam II-defined Lynch-related cancer cases with family history but is rare in other cancers: a summary of 1000 analyses.

BACKGROUND: Microsatellite instability (MSI) is a key marker for predicting the response of immune checkpoint inhibitors (ICIs) and for screening Lynch syndrome (LS). AIM: This study aimed to see the characteristics of cancers with high level of MSI (MSI-H) in genetic medicine and precision medicine. METHODS: This study analyzed the incidence of MSI-H in 1000 cancers and compared according to several clinical and demographic factors. RESULTS: The incidence of MSI-H was highest in endometrial cancers (26.7%, 20/75), followed by small intestine (20%, 3/15) and colorectal cancers (CRCs)(13.7%, 64/466); the sum of these three cancers (15.6%) was significantly higher than that of other types (2.5%)(P < 0.0001). MSI-H was associated with LS-related cancers (P < 0.0001), younger age (P = 0.009), and family history, but not with smoking, drinking, or serum hepatitis virus markers. In CRC cases, MSI-H was significantly associated with a family history of LS-related cancer (P < 0.0001), Amsterdam II criteria [odds ratio (OR): 5.96], right side CRCs (OR: 4.89), and multiplicity (OR: 3.31). However, MSI-H was very rare in pancreatic (0.6%, 1/162) and biliary cancers (1.6%, 1/64) and was null in 25 familial pancreatic cancers. MSI-H was more recognized in cancers analyzed for genetic counseling (33.3%) than in those for ICI companion diagnostics (3.1%)(P < 0.0001). Even in CRCs, MSI-H was limited to 3.3% when analyzed for drug use. CONCLUSIONS: MSI-H was predominantly recognized in LS-related cancer cases with specific family histories and younger age. MSI-H was limited to a small proportion in precision medicine especially for non-LS-related cancer cases.

Macroscopic visible core length can predict the histological sample quantity in endoscopic ultrasound-guided tissue acquisition: Multicenter prospective study.

OBJECTIVES: Measurement of the macroscopic visible core (MVC) length during macroscopic on-site quality evaluation (MOSE) may allow estimation of sample adequacy for next-generation sequencing (NGS), and prediction of correct diagnosis in endoscopic ultrasound-guided tissue acquisition (EUS-TA) of pancreatic masses. METHODS: This multicenter prospective study included consecutive patients who underwent EUS-TA for pancreatic masses using a 22-G Franseen needle. MVC length and pathological samples obtained from two needle passes were analyzed on a per-pass basis. Outcome measures included respective correlations of MVC length with histological sample quantity and diagnostic yields. RESULTS: The analysis included 204 passes from 102 EUS-TAs. MVC length correlated positively with histological sample quantity (P < 0.01). On the receiver operating characteristic curve for MVC length, the cut-off value and area under the curve for obtaining a candidate sample for NGS were 30 mm and 0.74 (95% confidence interval [CI] 0.65-0.83), respectively. On multivariate analysis, MVC length ≥30 mm was a significant factor affecting suitability for NGS (odds ratio 6.19; 95% CI 2.72-14.10). Histologic diagnostic yield correlated positively with MVC length (P = 0.01); however, there was no positive correlation between MVC length and overall (histology plus cytology) diagnostic yield. CONCLUSIONS: Measuring MVC length to predict histological sample quantity on MOSE may be of clinical significance during EUS-TA using a 22-G Franseen needle. It may be an effective method, particularly while submitting samples for NGS. REGISTRATION: University Hospital Medical Information Network Trials Registry (UMIN000036528).

Efficacy of endoscopic samplings during initial biliary drainage for cases of pancreatic head cancer: United diagnostic yields of multiple pathological samplings.

BACKGROUND/OBJECTIVES: The diagnostic ability of endoscopic ultrasound-guided fine needle aspiration (EUS-FNA) has been fully studied; however, the efficacy of other endoscopic samplings (OESs) is less clear. The aim of this study was to examine the diagnostic efficacies of OESs for pancreatic head cancer (PHC). METHODS: The diagnostic efficacies of endoscopic samplings were retrospectively analyzed in 448 PHC cases and 63 cases of mass-forming pancreatitis (MFP) during initial transpapillary biliary drainage. The OESs included duodenal biopsy (118 PHCs and 50 MFPs), biliary biopsy (218 and 51) with cytology (368 and 53), and pancreatic duct biopsy (23 and 13) with cytology (56 and 43). EUS-FNA was conducted in a different session (149 and 62). Factors associated with OES sensitivity were analyzed. The sensitivity of biliary biopsy was compared between 1.95 mm and 1.8 mm forceps. RESULTS: Cancer cells were confirmed in 87.9% of the EUS-FNA samplings and in 64.1% (268/418) obtained by combined OESs (average 1.7 OES types per case): 68.6% by duodenal biopsy, 59.6% by biliary biopsy, 32.6% by biliary cytology, 73.9% by pancreatic duct biopsy, and 33.9% by pancreatic duct cytology. No MFP cases revealed cancer by any sampling. OESs did not increase adverse events. Duodenal stenosis, serum bilirubin, tumor size, and pancreatic juice amounts were associated with OES sensitivity. Biliary biopsy had the same sensitivity with different forceps. CONCLUSION: EUS-FNA was the most diagnostic protocol; however, OESs can be safely applied during the initial biliary drainage to reduce the demand for EUS-FNA while providing good diagnostic yields.

Can regular follow-up imaging contribute to the determination of appropriate timing of surgery in patients with undiagnosed mucinous cystic neoplasm? A multicenter retrospective study.

OBJECTIVE: Guidelines suggest that patients with undiagnosed pancreatic cystic lesions should be monitored despite a lack of evidence supporting surveillance for undiagnosed mucinous cystic neoplasms (MCNs). We aimed to investigate the pre- and post-operative clinical course of patients with MCN and the utility of follow-up for patients who were not diagnosed with MCN at initial examination. PATIENTS AND METHODS: This multicenter retrospective study enrolled 28 patients with resected pathology-proven MCN; 12 and 16 patients underwent surgery within and after 6 months from the initial examination (Groups A and B, respectively). Outcome measures included changes in imaging findings until surgery in Group B, pathological findings between both groups and differences in pathological findings between patients with and without regular follow-up imaging in Group B. RESULTS: In Group B, the median cyst size was 30 and 48 mm at the initial examination and immediately before surgery, respectively. The incidence of mural cysts, thickened walls and mural nodules were 25, 19 and 0%, respectively, at the initial examination and 69, 56 and 31%, respectively, immediately before surgery. There were no significant differences in the invasive carcinoma rates between Groups A and B (13 vs. 17%). Regular follow-up imaging was offered to Group B. Among these, invasive carcinoma was found in one patient exhibiting no recurrence. One patient without follow-up imaging had invasive carcinoma recurrence post-operatively. CONCLUSIONS: MCNs increased in size, and typical imaging findings appeared over time. For undiagnosed MCN, regular follow-up examination contributed to the determination of the appropriate surgical timing.

Environmental impact of amino acids on the release of selenate immobilized in hydrotalcite: Integrated interpretation of experimental and density-functional theory study.

The environmental impact of amino acids on the release of SeO42- immobilized into hydrotalcite (Mg2Al-LDH) which belongs to the layered double hydroxides (LDHs) family was investigated by experimental study and the observed layer structure of hydrotalcite was verified through density-functional theory (DFT) calculations. Glycine, l-cysteine, and l-aspartic acid, which have smaller molecular sizes, can release SeO42- largely due to intercalation, unstabilization of Mg2Al-LDH and simple dissolution, while l-tryptophan and l-phenylalanine caused limited SeO42- release due to their larger sizes and aromaticity. XRD patterns for the solid residues after intercalation of amino acids revealed that the layer distance of Mg2Al-LDH was partially expanded. The main peaks and shoulder features corresponding to d003 diffraction were well explained by DFT simulations using glycine as a model: the layer spacing of the main peak is responsible for the remaining SeO42- and singly stacked glycine molecule and the layer spacing of the shoulder peak was well explained by doubly stacked glycine molecules. Hydrogen bonds between amino acids and hydroxyl ions in the metallic layers of Mg2Al-LDH were responsible for the stable configuration of the intercalated Mg2Al-LDH. This study indicates potential limitations to the stability of low-level radioactive wastes of 79Se in repositories which are affected by smaller molecules of amino acids released through degradation of organic matters in the pedosphere.

Detectability on Plain CT is an Effective Discriminator between Carcinoma and Benign Disorder for a Polyp >10 mm in the Gallbladder.

An appropriate diagnosis is required to avoid unnecessary surgery for gallbladder cholesterol polyps (GChPs) and to appropriately treat pedunculated gallbladder carcinomas (GCs). Generally, polyps >10 mm are regarded as surgical candidates. We retrospectively evaluated plain and contrast-enhanced (CE) computed tomography (CT) findings and histopathological features of 11 early GCs and 10 GChPs sized 10-30 mm to differentiate between GC and GChP >10 mm and determine their histopathological background. Patient characteristics, including polyp size, did not significantly differ between groups. All GCs and GChPs were detected on CE-CT; GCs were detected more often than GChPs on plain CT (73% vs 9%; p < 0.01). Sensitivity, specificity, positive and negative predictive values, and diagnostic accuracy for GCs were 73%, 90%, 89%, 75%, and 81%, respectively. On multivariate analysis, lesion detectability on plain CT was independently associated with GCs (odds ratio, 27.1; p = 0.044). Histopathologically, GChPs consisted of adipose tissue. Although larger vessel areas in GCs than in GChPs was not significant (52,737 µm2 vs 31,906 µm2; p = 0.51), cell densities were significantly greater in GCs (0.015/µm2 vs 0.0080/µm2; p < 0.01). Among GPs larger than 10 mm, plain CT could contribute to differentiating GCs from GChPs.

Application of enhancer of zeste homolog 2 immunocytochemistry to bile cytology.

BACKGROUND: Bile cytology has low diagnostic sensitivity and requires ancillary techniques. This study assessed the utility of enhancer of zeste homolog 2 (EZH2) immunocytochemistry (ICC) in bile cytology. METHODS: A total of 141 bile cytology specimens from 141 patients were evaluated retrospectively. Papanicolaou-stained slides were immunostained with an antibody to EZH2. After calculation of the EZH2 labeling index (LI), the cutoff value was determined via receiver operating characteristic curve analysis. Cytological performance with and without EZH2 ICC was evaluated with reference to the final diagnosis. RESULTS: The area under the curve for the EZH2 LI was 0.955, and the cutoff value for identifying benign bile samples versus malignant ones was 24.0%. The sensitivity and specificity values for malignancy were 53.4% and 100% for routine cytology only, 89.0% and 95.7% for EZH2 ICC only, and 89.8% and 95.7% for a combination of routine cytology and EZH2 ICC. The sensitivities of EZH2 ICC only and a combination of routine cytology and EZH2 ICC were significantly improved in comparison with routine cytology only (P < .001). EZH2 ICC alone had a sensitivity of 68.0% and a specificity of 85.7% in bile samples with atypical cytology, a sensitivity of 87.0% in samples that were suspicious for malignancy, and a sensitivity of 85.7% and a specificity of 100% in samples that were negative for malignancy. CONCLUSIONS: EZH2 ICC improved the diagnostic sensitivity for pancreatobiliary adenocarcinoma in bile cytology. This method is particularly meaningful in samples of indeterminate cytology and may be useful as an initial assessment to ensure that no cancer cells are missed.