The World Health Organization Reporting System for Pancreaticobiliary Cytopathology: Overview and Summary.

The recently published WHO Reporting System for Pancreaticobiliary Cytopathology (World Health Organization [WHO] System) is an international approach to the standardized reporting of pancreaticobiliary cytopathology, updating the Papanicolaou Society of Cytopathology System for Reporting Pancreaticobiliary Cytology (PSC System). Significant changes were made to the categorization of benign neoplasms, intraductal neoplasms, mucinous cystic neoplasms, and malignant neoplasms considered low grade. Benign neoplasms, such as serous cystadenoma, categorized as Neoplastic: benign in the PSC system, are categorized as Benign/negative for malignancy in the WHO system. Pancreatic neuroendocrine tumor, solid-pseudopapillary neoplasm, and gastrointestinal stromal tumor, categorized as Neoplastic: other in the PSC system, are categorized as Malignant in the WHO System in accord with their classification in the 5th edition WHO Classification of Digestive System Tumours (2019). The two new categories of Pancreaticobiliary Neoplasm Low-risk/grade and Pancreaticobiliary Neoplasm High-risk/grade are mostly limited to intraductal neoplasms and mucinous cystic neoplasms. Low-risk/grade lesions are mucinous cysts, with or without low-grade epithelial atypia. High-risk/grade lesions contain neoplastic epithelium with high-grade epithelial atypia. Correlation with clinical, imaging, and ancillary studies remains a key tenet. The sections for each entity are written to highlight key cytopathological features and cytopathological differential diagnoses with the pathologist working in low resource setting in mind. Each section also includes the most pertinent ancillary studies useful for the differential diagnosis. Sample reports are provided for each category. Finally, the book provides a separate section with risk of malignancy and management recommendations for each category to facilitate decision-making for clinicians.

A case of pancreatic PEComa with prominent inflammatory cell infiltration: the inflammatory subtype is a distinct histologic group of PEComa.

BACKGROUND: PEComa is a mesenchymal tumor that can occur in various organs including the uterus and soft tissues. PEComas are composed of perivascular epithelioid cells, and angiomyolipoma (AML), clear cell sugar tumor (CCST), and lymphangiomyomatosis (LAM) are considered lesions of the same lineage as tumors of the PEComa family. Histologically, a common PEComa shows solid or sheet-like proliferation of epithelioid cells. This is accompanied by an increase in the number of dilated blood vessels. Here, we report a case of pancreatic PEComa with marked inflammatory cell infiltration. CASE PRESENTATION: A 74-year-old male patient underwent an appendectomy for acute appendicitis. Postoperative computed tomography and magnetic resonance imaging revealed a 30 × 25 mm non-contrast-enhanced circular lesion in the tail of the pancreas. The imaging findings were consistent with a malignant tumor, and distal pancreatectomy was performed. Histologically, most area of the lesion was infiltrated with inflammatory cells. A few epithelioid cells with large, round nuclei, distinct nucleoli, and eosinophilic granular cytoplasm were observed. Spindle-shaped tumor cells were observed. Delicate and dilated blood vessels were observed around the tumor cells. Immunohistochemically, the atypical cells were positive for αSMA, Melan A, HMB-45, and TFE3. The cytological characteristics of the tumor cells and the results of immunohistochemical staining led to a diagnosis of pancreatic PEComa. CONCLUSIONS: A histological variant known as the inflammatory subtype has been defined for hepatic AML. A small number of tumor cells present with marked inflammatory cell infiltration, accounting for more than half of the lesions, and an inflammatory myofibroblastic tumor-like appearance. To our knowledge, this is the first report of pancreatic PEComa with severe inflammation. PEComa is also a generic term for tumors derived from perivascular epithelioid cells, such as AML, CCST, and LAM. Thus, this case is considered an inflammatory subtype of PEComa. It has a distinctive morphology that is not typical of PEComa. This histological phenotype should be widely recognized.

The significance of Hippo pathway protein expression in oral squamous cell carcinoma.

Introduction: The Hippo pathway consists of mammalian sterile 20-like kinase 1/2 (MST1/2), large tumor suppressor 1/2 (LATS1/2), and yes-associated protein (YAP)1. Herein, we present the first report on the significance of major Hippo pathway protein expression in oral squamous cell carcinoma (OSCC). Methods: The analyses included oral epithelial dysplasia (OED, n = 7), carcinoma in situ (CIS, n = 14), and oral squamous cell carcinoma (OSCC, n = 109). Results: Cytoplasmic expression of MST1, LATS1, and LATS2 was low in OED, CIS, and OSCC. The cytoplasmic expression of MST2 was high in OED (5/7 cases), CIS (9/14 cases), and poorly differentiated OSCC (8/8 cases) but was low/lost in a proportion of differentiated OSCC (60/101 cases). The expression of YAP1 was associated with differentiation; low YAP expression was significantly more frequent in well-differentiated OSCC (35/71 cases), compared to moderately and poorly differentiated OSCC (11/38 cases). An infiltrative invasion pattern was associated with a high expression of MST2 and high expression of YAP1. The high expression of YAP1 was associated with features of epithelial-to-mesenchymal transition (EMT), such as the loss of E-cadherin and high expression of vimentin, laminin 5, and Slug. High expression of protein arginine methyltransferase (PRMT) 1 or 5, which positively regulates YAP activity, was associated with the high expression of YAP1 (p < 0.0001). Conclusion: Among the major Hippo pathway proteins, MST2 displayed a distinctive expression pattern in a significant proportion of differentiated OSCC, suggesting a possible differential role for MST2 depending on the course of OSCC progression. A high YAP1 expression may indicate aggressive OSCC with EMT via PRMTs at the invasive front.

Multicenter prospective randomized controlled clinical trial comparing the pocket-creation method with and without single-clip traction of colonic endoscopic submucosal dissection.

BACKGROUND: The pocket-creation method (PCM) was developed to overcome the technical difficulties of endoscopic submucosal dissection (ESD), although opening the pocket remains challenging. We developed a novel technique of PCM with single-clip traction (PCM-CT), which uses a reopenable clip as a traction device to maintain stability during the procedure. No prospective study has compared the efficacy of PCM-CT and PCM. This study aimed to investigate the effectiveness of PCM-CT vs. PCM in a randomized controlled trial. METHODS: This randomized controlled clinical trial was conducted at four Japanese institutions. Patients with superficial colorectal neoplastic lesions were included following Japanese guidelines for colorectal cancer. Seven moderately experienced endoscopists performed the ESD procedures using either PCM-CT or PCM. RESULTS: 100 patients were enrolled in the study. Compared with PCM, PCM-CT achieved significantly faster mean (SD) dissection speed (21.4 [10.8] vs. 27.0 [14.5] mm2/min [95%CI 0.5 to 10.7], P = 0.03), and reduced the mean procedure time (81.8 [57.9] vs. 64.8 [47.6] minutes [95%CI -38.2 to 4.3], P = 0.12) and pocket-opening time (37.8 [33.0] vs. 30.0 [28.9] minutes [95%CI -20.2 to 4.6], P = 0.22). En bloc and R0 resection rates were not significantly different between the two groups (100% vs. 100%, P >0.99; 100% vs. 96%, P = 0.50, respectively). No significant differences were observed in adverse events between the two groups. CONCLUSION: ESD facilitated by the novel PCM-CT method appeared to be significantly faster than PCM. Both methods achieved high R0 resection rates.

Immune Checkpoint Inhibitor-induced Pancreatitis with Pancreatic Enlargement Mimicking Autoimmune Pancreatitis: A Case Report and Review of the Literature.

A 61-year-old woman was administered 35 cycles of pembrolizumab for the treatment of recurrent endometrial cancer, achieving a complete response. She presented with asymptomatic pancreatic enlargement and elevated hepatobiliary enzymes, but amylase and lipase levels were within the normal ranges. Intrapancreatic bile duct stenosis due to pancreatic enlargement was present, mimicking autoimmune pancreatitis on computed tomography performed before the onset of clinical manifestations. A histological examination of a biopsy specimen showed lymphocyte and plasma cell infiltration with dense fibrosis in the stroma. The patient was successfully treated with oral prednisolone. There were no manifestations of recurrent pancreatitis after tapering the prednisolone dose.

H3K27me3 deficiency in dedifferentiated carcinoma and carcinosarcoma of the endometrium.

The present study immunohistochemically investigated trimethylation of lysine 27 of histone 3 (H3K27me3) expression in 769 endometrial carcinomas and 196 uterine mesenchymal tumors. One dedifferentiated endometrial carcinoma (DEC) and one carcinosarcoma showed H3K27me3 deficiency that was limited to undifferentiated and sarcomatous components, respectively. Switch/sucrose nonfermenting (SWI/SNF) complex subunits (SMARCA4, SMARCB1, and ARID1A/1B) and mismatch repair proteins were proficient in both tumors. The dimethylation of H3K27 (H3K27me2) was deficient in the undifferentiated component, whereas the sarcomatous component had scattered H3K27me2-positive cells. CXorf67, which inhibits PRC2 function, was diffusely expressed in the sarcomatous component. CXorf67 was negative in the undifferentiated component, which was submitted to a genetic analysis and showed no alterations in PRC2 core subunits or H3K27. The present results suggest H3K27 methylation dysregulation as a cause of SWI/SNF-proficient DEC and carcinosarcoma and imply differences in their level of and the mechanisms underlying H3K27 methylation dysregulation.

Systematic review of challenging issues in pathology of intraductal papillary mucinous neoplasms.

BACKGROUND: Intraductal papillary mucinous neoplasms (IPMNs) are a cystic precursor to pancreatic cancer. IPMNs deemed clinically to be at high-risk for malignant progression are frequently treated with surgical resection, and pathological examination of the pancreatectomy specimen is a key component of the clinical care of IPMN patients. METHODS: Systematic literature reviews were conducted around eight topics of clinical relevance in the examination of pathological specimens in patients undergoing resection of IPMN. RESULTS: This review provides updated perspectives on morphological subtyping of IPMNs, classification of intraductal oncocytic papillary neoplasms, nomenclature for high-grade dysplasia, assessment of T stage, distinction of carcinoma associated or concomitant with IPMN, role of molecular assessment of IPMN tissue, role of intraoperative assessment by frozen section, and preoperative evaluation of cyst fluid cytology. CONCLUSIONS: This analysis provides the foundation for data-driven approaches to several challenging issues in the pathology of IPMNs.

Neonatal onset of Niemann-Pick disease type C in a patient with cholesterol re-accumulation in the transplanted liver and inflammatory bowel disease.

BACKGROUND: Niemann-Pick disease type C (NPC) is an autosomal recessive inherited and neurodegenerative disorder. Approximately 10% of NPC patients have acute liver failure and sometimes need liver transplantation (LT), and 7% reportedly develop inflammatory bowel disease (IBD). We report the case of a girl with NPC who had a re- accumulation of cholesterol in the transplanted liver and NPC-related IBD. CASE REPORT: The patient underwent living donor liver transplantation (LDLT) due to severe acute liver failure caused by an unknown etiology inherited from her father. At 1 year and 6 months (1Y6M), she developed neurological delay, catalepsy, and vertical supranuclear gaze palsy. The foam cells were found in her skin, and fibroblast Filipin staining was positive; hence, she was diagnosed with NPC. It was identified that her father had NPC heterozygous pathogenic variant. At 2 years, she had anal fissure, skin tag and diarrhea. She was diagnosed with NPC-related IBD, using a gastrointestinal endoscopy. Three years after LT, liver biopsy revealed foam cells and numerous fatty droplets. At 8 years, broken hepatocytes and substantial fibrosis were observed. She died from circulation failure due to hypoalbuminemia at 8Y2M. CONCLUSIONS: In NPC, load of cholesterol metabolism is suggested to persist even after LT. LDLT from NPC heterozygous variant donor was insufficient to metabolize cholesterol overload. In NPC patients, the possibility of cholesterol re-accumulation should be considered when LT is performed. NPC-related IBD should be considered when NPC patients have anorectal lesions or diarrhea.

The Ki67 index evaluation of pancreatic neuroendocrine tumors using 3D immunohistochemistry in small tissue specimens.

BACKGROUND: /Objectives: This study aimed to evaluate the usefulness of three-dimensional (3D) immunohistochemistry for the Ki67 index of small tissue specimens of pancreatic neuroendocrine tumor (PanNET). METHODS: Clinicopathological materials from 17 patients with PanNET who underwent surgical resection at Jichi Medical University Hospital were analyzed. We compared the Ki67 index of endoscopic ultrasonography-fine-needle aspiration biopsy (EUS-FNAB) specimens, surgical specimens, and small tissue specimens hollowed from paraffin blocks of surgical specimens that were substituted for EUS-FNAB specimens ("sub-FNAB"). The sub-FNAB specimens were optically cleared using LUCID (IlLUmination of Cleared organs to IDentify target molecules) and analyzed using 3D immunohistochemistry. RESULTS: The median Ki67 index in FNAB, sub-FNAB, and surgical specimens with conventional immunohistochemistry were 1.2% (0.7-5.0), 2.0% (0.5-14.6), and 5.4% (1.0-19.4), respectively. The median Ki67 index in sub-FNAB specimens with tissue clearing was calculated separately using the total number of cells on multiple images ("multiple slice"), with the image of the fewest positive cells ("coldspot"), and with the image of most positive cells ("hotspot"), which were 2.7% (0.2-8.2), 0.8% (0-4.8), and 5.5% (2.3-12.4), respectively. PanNET grade evaluated for the hotspot of the surgical specimens was significantly more consistent with those of the hotspot than multiple images of sub-FNAB specimens (16/17 vs. 10/17, p = 0.015). Hotspot evaluation using 3D immunohistochemistry of the sub-FNAB specimens showed agreement with the assessment of the surgical specimens (Kappa coefficient: 0.82). CONCLUSIONS: Tissue clearing and 3D immunohistochemistry for the Ki67 index can potentially improve the preoperative evaluation of EUS-FNAB specimens of PanNET in routine clinical practice.

Cholangiocarcinoma Resembling IgG4-related Sclerosing Cholangitis.

A 66-year-old man diagnosed with immunoglobulin G4-related sclerosing cholangitis (IgG4-SC) with diffuse intrahepatic bile duct stenosis and elevated serum IgG4 levels was referred for a further examination because of elevated serum carbohydrate antigen 19-9 levels despite treatment with corticosteroids. An umbilical nodule was found on a physical examination and a biopsy showed adenocarcinoma. Although several imaging studies revealed no changes from prior studies, bile cytology collected by endoscopic retrograde cholangiopancreatography showed adenocarcinoma. Consequently, the patient was diagnosed with cholangiocarcinoma resembling IgG4-SC after detecting an umbilical metastasis, also known as Sister Mary Joseph's nodule.

A brief review of the WHO reporting system for pancreaticobiliary cytopathology.

The World Health Organization (WHO), the International Academy of Cytology, and the International Agency for Research on Cancer have developed an approach to standardized reporting of pancreaticobiliary cytopathology. The WHO Reporting System for Pancreaticobiliary Cytopathology (WHO System) revises the Papanicolaou Society of Cytopathology (PSC) System for Reporting Pancreaticobiliary Cytology published in 2015 and replaces the 6 PSC categories with 7 categories: "Insufficient/Inadequate/Nondiagnostic"; "Benign/Negative for malignancy"; "Atypical"; "Pancreaticobiliary neoplasm, low risk/grade (PaN-low)"; "Pancreatic neoplasm, high risk/grade (PaN-High)"; "Suspicious for malignancy"; and "Malignant". In the PSC system, there is a single category for "Neoplastic" lesions that includes 2 groups, 1 for benign neoplasms and 1 named "Neoplastic-other", dominated by premalignant intraductal neoplasms primarily intraductal papillary mucinous neoplasms and low-grade malignant neoplasms (pancreatic neuroendocrine tumors (PanNET) and solid pseudopapillary neoplasms (SPN). In the WHO System, benign neoplasms with virtually no risk of malignancy are included in the "Benign" category and low-grade malignancies (PanNET and SPN) are included in the "Malignant" category, as per the 5th edition of the WHO Classification of Digestive System Tumors, while the non-invasive pre-malignant lesions of the ducts are divided by the cytomorphological grade of the epithelium into PaN-low and PaN-high with distinctly different risks of malignancy. Within each category, key diagnostic cytopathologic features and the ancillary studies for diagnostic and prognostic evaluation, as well as the implications of diagnosis for patient care and management, are outlined. Reporting and diagnostic management options recognize the variations in the availability of diagnostic and prognostic ancillary testing modalities in low- and middle-income countries.

Patient-derived spheroids and patient-derived organoids simulate evolutions of lung cancer.

Cancer cells harbor many genetic mutations and gene expression profiles different from normal cells. Patient-derived cancer cells (PDCC) are preferred materials in cancer study. We established patient-derived spheroids (PDSs) and patient-derived organoids (PDOs) from PDCCs isolated from the malignant pleural effusion in 8 patients. The morphologies suggested that PDSs may be a model of local cancer extensions, while PDOs may be a model of distant cancer metastases. The gene expression profiles differed between PDSs and PDOs: Gene sets related to inflammatory responses and EMT were antithetically regulated in PDSs or in PDOs. PDSs demonstrated an attenuation of the pathways that contribute to the enhancement of transforming growth factor beta (TGF-ß) induced epithelial mesenchymal transition (EMT), while PDOs demonstrated an attenuation of it. Taken together, PDSs and PDOs have differences in both the interaction to the immune systems and to the stroma. PDSs and PDOs will provide a model system that enable intimate investigation of the behavior of cancer cells in the body.

A case of vasoactive intestinal peptide-secreting tumor (VIPoma) arising from MEN1 inactivation which recurred 15 years after the initial resection.

Vasoactive intestinal peptide-secreting tumors (VIPomas) are extremely rare functional pancreatic neuroendocrine neoplasms (p-NENs) characterized by watery diarrhea, hypokalemia, and achlorhydria. Here, we report the case of a 51-year-old female patient with VIPoma that recurred after a long-term disease-free interval. This patient had been asymptomatic for approximately 15 years after the initial curative surgery for pancreatic VIPoma, with no metastasis. The patient underwent a second curative surgery for the locally recurrent VIPoma. Whole-exome sequencing of the resected tumor revealed a somatic mutation in MEN1, which is reportedly responsible not only for multiple endocrine neoplasia type 1 (MEN1) syndrome but also sporadic p-NENs. Symptoms were controlled with lanreotide before and after surgery. The patient is alive with no relapse following 14 months after surgery. This case demonstrates the importance of long-term observation of patients with VIPoma.

The World Health Organization Reporting System for Pancreaticobiliary Cytopathology.

The World Health Organization (WHO), the International Academy of Cytology, and the International Agency for Research on Cancer, with expert contributors from around the world, present an international approach to standardized reporting of pancreaticobiliary cytopathology. This reporting system is one of the first in a series from various body sites that mirror the WHO Classification of Tumours series and provides an evidence-based terminology system with associated risk of malignancy and diagnostic management recommendation per diagnostic category. The WHO Reporting System for Pancreaticobiliary Cytopathology (WHO system) revises the Papanicolaou Society of Cytopathology (PSC) system for Reporting Pancreaticobiliary Cytology published in 2015 and replaces the six-tiered system with a seven-tiered system: "insufficient/inadequate/nondiagnostic"; "benign (negative for malignancy)," "atypical," "pancreaticobiliary neoplasm of low risk/low grade," "pancreatic neoplasm of high risk/high grade," "suspicious for malignancy," and "malignant." The principal differences between the WHO and the PSC systems revolve around the classification of neoplasia. In the PSC system, there was a single category for "neoplastic" lesions that includes two groups, one for "benign neoplasms" [primarily serous cystadenoma] and one named "other," dominated by premalignant intraductal neoplasms (primarily intraductal papillary mucinous neoplasms) and low-grade malignant neoplasms [pancreatic neuroendocrine tumors (PanNETs) and solid pseudopapillary neoplasms (SPNs)]. In the WHO system, benign neoplasms with virtually no risk of malignancy are included in the "benign" category and low-grade malignancies (PanNET and SPN) are included in the "malignant" category, as per the WHO Classification of Digestive System Tumours, thus leaving in the "neoplasm" category primarily those noninvasive premalignant lesions of the ductal system. These neoplasms are divided by the cytomorphological grade of the epithelium into low risk/low-grade and high risk/high-grade, with distinctly different risks of malignancy. As with the PSC system, the WHO system advocates close correlation with imaging and encourages incorporation of ancillary testing into the final diagnosis, such as biochemical (CEA and amylase) and molecular testing of cyst fluid and bile duct brushings. Key diagnostic cytopathological features of specific lesions or neoplasms, ancillary studies for diagnostic and prognostic evaluation, and implications of diagnosis for patient care and management are discussed. In addition, the WHO system includes reporting and diagnostic management options that recognize the variations in the availability of diagnostic and prognostic ancillary testing modalities in low- and middle-income countries, where cytopathology is particularly useful and is increasingly available in the absence of histopathological services.

Performance of an artificial intelligence-based diagnostic support tool for early gastric cancers: Retrospective study.

OBJECTIVES: Endoscopists' abilities to diagnose early gastric cancers (EGCs) vary, especially between specialists and nonspecialists. We developed an artificial intelligence (AI)-based diagnostic support tool "Tango" to differentiate EGCs and compared its performance with that of endoscopists. METHODS: The diagnostic performances of Tango and endoscopists (34 specialists, 42 nonspecialists) were compared using still images of 150 neoplastic and 165 non-neoplastic lesions. Neoplastic lesions included EGCs and adenomas. The primary outcome was to show the noninferiority of Tango (based on sensitivity) over specialists. The secondary outcomes were the noninferiority of Tango (based on accuracy) over specialists and the superiority of Tango (based on sensitivity and accuracy) over nonspecialists. The lower limit of the 95% confidence interval (CI) of the difference between Tango and the specialists for sensitivity was calculated, with >-10% defined as noninferiority and >0% defined as superiority in the primary outcome. The comparable differences between Tango and the endoscopists for each performance were calculated, with >10% defined as superiority and >0% defined as noninferiority in the secondary outcomes. RESULTS: Tango achieved superiority over the specialists based on sensitivity (84.7% vs. 65.8%, difference 18.9%, 95% CI 12.3-25.3%) and demonstrated noninferiority based on accuracy (70.8% vs. 67.4%). Tango achieved superiority over the nonspecialists based on sensitivity (84.7% vs. 51.0%) and accuracy (70.8% vs. 58.4%). CONCLUSIONS: The AI-based diagnostic support tool for EGCs demonstrated a robust performance and may be useful to reduce misdiagnosis.

[Surgical Case of the Primary Pulmonary Leiomyosarcoma:Report of a Case].

A 70-year-old man was referred for an abnormal chest shadow. Enhanced computed tomography (CT) revealed a well-circumscribed lung tumor of 53 mm in diameter in the left upper lobe with slight enhancement. Positron emission tomography-CT showed a high maximum standardized uptake value for the tumor but no metastasis in the lymph nodes or other organs. Although a definitive diagnosis could not be made by transbronchial biopsy, the tumor was highly suspected to be malignant based on the radiological findings, and a left upper lobectomy with mediastinal lymph nodes dissection was performed for definitive diagnosis and treatment. A pathological examination showed the tumor to be composed of mitotic spindle-shaped cells, which were positive for α-smooth muscle actin, desmin, and caldesmon. The MIB-1 labelling index was 60~70%. According to these pathologic findings, the tumor was identified as a leiomyosarcoma. Metastases to the skin of chest and hilar lymph nodes were noted six months after the surgery for which radiotherapy was performed.

New digital confocal laser microscopy may boost real-time evaluation of endoscopic ultrasound-guided fine-needle biopsy (EUS-FNB) from solid pancreatic lesions: Data from an international multicenter study.

BACKGROUND: Pancreatic cancer is an aggressive malignancy and a leading cause of cancer death worldwide; its lethality is partly linked to the difficulty of early diagnosis. Modern devices for endoscopic ultrasound-guided fine-needle biopsy (EUS-FNB) were recently developed to improve targeting and sampling of small lesions, but innovative technologies for microscopic assessment are still lacking. Ex vivo fluorescence confocal laser microscopy (FCM) is a new digital tool for real-time microscopic assessment of fresh unfixed biological specimens, avoiding conventional histological slide preparation and potentially being highly appealing for EUS-FNB specimens. METHODS: This study evaluated the possible role of FCM for immediate evaluation of pancreatic specimens from EUS-FNB. It involved comparison of the interobserver agreement between the new method and standard histological analysis during international multicenter sharing of digital images. Digital images from 25 cases of EUS-FNB obtained with real-time FCM technology and 25 paired digital whole-slide images from permanent conventional paraffin sections were observed by 10 pathologists from different Institutions in Europe, Japan, and the United States, in a blinded manner. The study evaluated 500 observations regarding adequacy, morphological clues, diagnostic categories, and final diagnosis. FINDINGS: Statistical analysis showed substantial equivalence in the interobserver agreement among pathologists using the two techniques. There was also good inter-test agreement in determining sample adequacy and when assigning a diagnostic category. Among morphological features, nuclear enlargement was the most reproducible clue, with very good inter-test agreement. INTERPRETATION: Findings in this study are from international multicenter digital sharing and are published here for the first time. Considering the advantages of FCM digital diagnostics in terms of reduced time and unaltered sample maintenance, the ex vivo confocal laser microscopy may effectively improve traditional EUS-FNB diagnostics, with significant implications for planning modern diagnostic workflow for pancreatic tumors. FUNDING: This study was not supported by any funding source.

Histopathological tumour response scoring in resected pancreatic cancer following neoadjuvant therapy: international interobserver study (ISGPP-1).

BACKGROUND: Most tumour response scoring systems for resected pancreatic cancer after neoadjuvant therapy score tumour regression. However, whether treatment-induced changes, including tumour regression, can be identified reliably on haematoxylin and eosin-stained slides remains unclear. Moreover, no large study of the interobserver agreement of current tumour response scoring systems for pancreatic cancer exists. This study aimed to investigate whether gastrointestinal/pancreatic pathologists can reliably identify treatment effect on tumour by histology, and to determine the interobserver agreement for current tumour response scoring systems. METHODS: Overall, 23 gastrointestinal/pancreatic pathologists reviewed digital haematoxylin and eosin-stained slides of pancreatic cancer or treated tumour bed. The accuracy in identifying the treatment effect was investigated in 60 patients (30 treatment-naive, 30 after neoadjuvant therapy (NAT)). The interobserver agreement for the College of American Pathologists (CAP) and MD Anderson Cancer Center (MDACC) tumour response scoring systems was assessed in 50 patients using intraclass correlation coefficients (ICCs). An ICC value below 0.50 indicated poor reliability, 0.50 or more and less than 0.75 indicated moderate reliability, 0.75 or more and below 0.90 indicated good reliability, and above 0.90 indicated excellent reliability. RESULTS: The sensitivity and specificity for identifying NAT effect were 76.2 and 49.0 per cent respectively. After NAT in 50 patients, ICC values for both tumour response scoring systems were moderate: 0.66 for CAP and 0.71 for MDACC. CONCLUSION: Identification of the effect of NAT in resected pancreatic cancer proved unreliable, and interobserver agreement for the current tumour response scoring systems was suboptimal. These findings support the recently published International Study Group of Pancreatic Pathologists recommendations to score residual tumour burden rather than tumour regression after NAT.