Dichotomy in intrahepatic cholangiocarcinomas based on histologic similarities to hilar cholangiocarcinomas

Classification of intrahepatic cholangiocarcinoma

Cholangiocarcinoma is a heterogenous malignancy with various classifications based on location, morphological features, histological features, and actionable genetic mutations. Intrahepatic cholangiocarcinoma (ICC), which arises in and proximal to second order bile ducts, is the second most common primary liver malignancy after hepatocellular carcinoma. In this review, we will discuss ICC risk factors, precursor lesions, various growth, anatomic, morphologic, and histologic classifications, rare variants, and differential diagnoses.

Pathologic and Molecular Features of Perihilar Cholangiocarcinoma Based on U-P Point Division

CONTEXT.—

The Japanese Society of Hepato-Biliary-Pancreatic Surgery guidelines propose a classification scheme that differs from the Union for International Cancer Control (UICC) system, in which the anatomic U-P point is the boundary between intrahepatic cholangiocarcinoma and perihilar cholangiocarcinoma (PCC).

OBJECTIVE.—

To investigate whether this classification system improves clinicopathologic and genomic differentiation.

DESIGN.—

Fifty-eight PCC cases defined by the UICC system were collected and classified into intrahepatic PCC (IPCC) and extrahepatic PCC (EPCC) categories using U-P point division. They were analyzed by next-generation sequencing using a panel that targeted 425 cancer-related genes.

RESULTS.—

The IPCC group exhibited a significantly larger tumor size compared with the EPCC group (4.67 ± 2.44 cm versus 2.50 ± 0.91 cm, P = .002). The mutation frequency of the KRAS proto-oncogene, GTPase (KRAS) Q61 was also significantly higher in the IPCC group than in the EPCC group (16.7% versus 0.0%, P = .03). There were no statistically significant differences in other pathologic features or genomic characteristics, including tumor mutation burden and microsatellite instability. Significant differences in gene mutation rates, such as phosphatidylinositol-4,5-bisphosphate 3-kinase catalytic subunit alpha (PIK3CA; 0.0% versus 15.8%, P = .01) and tumor protein p53 (TP53; 34.5% versus 63.2%, P = .04), were observed between PCC and adjacent biliary tract cancers.

CONCLUSIONS.—

This study offers valuable insight into the clinicopathologic and genomic features of PCC. It is proposed that the U-P point division may have limited potential to refine the characterization of PCC regarding these features, and that the UICC classification system can readily demonstrate the molecular specificity of PCC.

Combined analysis of albumin in situ hybridisation and C reactive protein immunohistochemistry for the diagnosis of intrahepatic cholangiocarcinoma: towards a molecular classification paradigm

AIMS

Intrahepatic cholangiocarcinoma (iCCA) is a diagnosis of exclusion that can pose a challenge to the pathologist despite thorough clinical workup. Although several immunohistochemical markers have been proposed for iCCA, none of them reached clinical practice. We here assessed the combined usage of two promising diagnostic approaches, albumin in situ hybridisation (Alb-ISH) and C reactive protein (CRP) immunohistochemistry, for distinguishing iCCA from other adenocarcinoma primaries.

METHODS

We conducted Alb-ISH and CRP immunohistochemistry in a large European iCCA cohort (n=153) and compared the results with a spectrum of other glandular adenocarcinomas of different origin (n=885). In addition, we correlated expression patterns with clinicopathological information and mutation data.

RESULTS

Alb-ISH was highly specific for iCCA (specificity 98.8%) with almost complete negativity in perihilar CCA and only rare positives among other adenocarcinomas (sensitivity 69.5%). CRP identified the vast majority of iCCA cases (sensitivity 84.1%) at a lower specificity of 86.4%. Strikingly, the combination of CRP and Alb-ISH boosted the diagnostic sensitivity to 88.0% while retaining a considerable specificity of 86.1%. Alb-ISH significantly correlated with CRP expression, specific tumour morphologies and small or large duct iCCA subtypes. Neither Alb-ISH nor CRP was associated with iCCA patient survival. 16 of 17 recurrent mutations in either IDH1, IDH2 and FGFR2 affected Alb-ISH positive cases, while the only KRAS mutation corresponded to an Alb-ISH negative case.

CONCLUSIONS

In conclusion, we propose a sequential diagnostic approach for iCCA, integrating CRP immunohistochemistry and Alb-ISH. This may improve the accuracy of CCA classification and pave the way towards a molecular-guided CCA classification.

Morphologic and immunohistochemical characterization of small and large duct cholangiocarcinomas in a Western cohort: A panel of pCEA, CRP, N-cadherin, and albumin in situ hybridization aids in subclassification

Two morphologic subtypes of intrahepatic cholangiocarcinoma (iCCA), small duct and large duct, are now recognized, and importantly, these subtypes are associated with distinct molecular pathways and therapeutic options. Initial studies demonstrated the feasibility of morphologic subclassification and helped characterize the immunoprofile of the subtypes. However, few studies have been undertaken in Western countries where incidence of the subtypes is likely distinct from that in the East. To address this, 48 tumors from a North American cohort, consisting of 29 iCCAs, 18 extrahepatic CCAs (eCCAs), and 1 tumor of unclear origin (liver vs. gallbladder growing into liver) were classified by morphologic criteria as large duct (19 tumors), small duct (13 tumors), or indeterminate (13 tumors; all iCCAs). Notably, only 3 iCCAs were classified as large duct. Additionally, we evaluated the utility of common biomarkers to aid in subclassification, given that a significant portion of iCCAs were challenging to classify (e.g., indeterminate morphology). Tumors were screened for expression of mucicarmine, epithelial membrane antigen (EMA), monoclonal (mCEA), polyclonal CEA (pCEA), N-cadherin, CD56, and albumin by in situ hybridization (ALB-ISH). Of these, pCEA, CRP, N-cadherin, and ALB-ISH showed statistically significant differences between large and small duct types (P < 0.0028), with high specificity (≥88 %) and at least moderate sensitivity (≥60 %). Eleven of the 13 morphologically indeterminate tumors could be classified based on their expression of these 4 markers. Four additional large duct iCCAs were subsequently obtained from a second North American institution and assessed for pCEA, N-cadherin, and albumin expression. Combining these data with the initial cohort of large duct iCCAs (total of 7 large duct iCCAs) showed similar biomarker associations. In conclusion, in this Western cohort, 55 % of iCCAs (16 of 29) could be subclassified as large or small duct type based on morphology alone. With the aid of the 4-marker panel, 93 % of iCCAs (27 of 29) could be classified. Unlike in East Asian cohorts, the vast majority of iCCAs (88 %) was small duct type, and hepatolithiasis was not observed. CRP, N-cadherin, and ALB-ISH were found to be specific for small duct iCCA, whereas diffuse, strong expression of pCEA showed specificity for large duct tumors. This is the first report to highlight the utility of pCEA to subclassify iCCAs. Additionally, in cases in which the primary site (within the biliary tract) was unclear, CRP, ALB-ISH, N-cadherin, and pCEA were helpful in distinguishing iCCA from eCCA.

Update for: New developments in systemic therapy for advanced biliary tract cancer

Biliary tract cancer, carcinoma of the extrahepatic bile ducts, carcinoma of the gallbladder, ampullary carcinoma, and intrahepatic cholangiocarcinoma are often identified at advanced stages. The standard therapy for advanced biliary tract cancer has been a combination of cytotoxic agents. Globally, gemcitabine plus cisplatin has been the standard first-line regimen, whereas gemcitabine plus cisplatin plus S-1 and gemcitabine plus S-1 have also been the standard regimens in Japan. Recently, treatment strategies have been updated. As first-line systemic therapy, the addition of an immune checkpoint inhibitor, such as durvalumab or pembrolizumab, to gemcitabine plus cisplatin has been shown to prolong overall survival compared with gemcitabine plus cisplatin. These combined immunotherapies are widely used in clinical practice as internationally standard first-line regimens. Regarding second-line treatment after a gemcitabine-based regimen, fluorouracil and folinic acid plus oxaliplatin have been the standard regimen. Additionally, FGFR2 fusion gene/rearrangement, mutations of IDH1/2, KRAS, and BRAF, and overexpression of HER2 are promising therapeutic targets for which the effectiveness of each targeted therapy has been reported, at this time, as a second-line or later treatment.

Hepatic Stellate Cells Functional Heterogeneity in Liver Cancer

Hepatic stellate cells (HSCs) are the liver's pericytes, and play key roles in liver homeostasis, regeneration, fibrosis, and cancer. Upon injury, HSCs activate and are the main origin of myofibroblasts and cancer-associated fibroblasts (CAFs) in liver fibrosis and cancer. Primary liver cancer has a grim prognosis, ranking as the third leading cause of cancer-related deaths worldwide, with hepatocellular carcinoma (HCC) being the predominant type, followed by intrahepatic cholangiocarcinoma (iCCA). Moreover, the liver hosts 35% of all metastatic lesions. The distinct spatial distribution and functional roles of HSCs across these malignancies represent a significant challenge for universal therapeutic strategies, requiring a nuanced and tailored understanding of their contributions. This review examines the heterogeneous roles of HSCs in liver cancer, focusing on their spatial localization, dynamic interactions within the tumor microenvironment (TME), and emerging therapeutic opportunities, including strategies to modulate their activity, and harness their potential as targets for antifibrotic and antitumor interventions.

Molecular subtypes of intrahepatic cholangiocarcinoma

Intrahepatic cholangiocarcinoma (iCCA) presents in two clinically distinct subtypes: large duct (LD-iCCA) and small duct (SD-iCCA). These subtypes exhibit significant molecular, genetic, and histopathological differences that impact patient prognosis and treatment responsiveness. This review advocates for a subtype-specific approach to iCCA research and clinical management, including tailored therapeutic strategies that consider distinct genetic profiles and tumor microenvironments. Current therapeutic approaches hold promise, yet efficacy varies by subtype. Additionally, subtype-specific molecular diagnostics, including DNA methylation-based classifiers and transcriptomic sequencing, have shown potential in refining iCCA subclassification, thereby guiding precision medicine efforts. This article outlines existing clinical trials, key research trajectories, and future directions for developing more effective subtype-adapted therapies for iCCA.

Standardizing the reporting of cholangiocarcinoma: the society of abdominal radiology disease focused panel on cholangiocarinoma lexicon

In March 2023, the Society of Abdominal Radiology (SAR) Disease Focused Panel (DFP) on Cholangiocarcinoma (CCA) was formed. One of its initial tasks was for creation of a lexicon specific for CCA to complement the terms related to the Liver Imaging Reporting and Data System (LI-RADS) category M. A committee was formed and vetted 15 unique terms for CCA. The multidisciplinary members of the DFP passed each term by over 90% approval. The purpose of this paper is to describe the process for developing the lexicon, introduce the lexicon terms, and provide a pictorial atlas of the 15 vetted terms relating to the imaging findings of CCA.

Surgical interpretation of the WHO subclassification of intrahepatic cholangiocarcinoma: a narrative review

Intrahepatic cholangiocarcinoma (iCCA) has been subclassified by its gross morphology into the mass-forming (MF), periductal-infiltrating (PI), and intraductal growth (IG) types and their combinations. This classification correlates well with clinical features; for example, MF-iCCA has less lymph-node metastasis and a better prognosis than PI-iCCA. According to the recently accumulated evidence from histological investigations, the WHO classification endorsed a subclassification scheme in which iCCA cases are classified into small- and large-duct types. Small-duct iCCA is considered to originate from septal or smaller bile ducts and is characterized by less frequent lymph-node metastasis, a favorable prognosis, and an MF appearance. Large-duct iCCA arises around the second branch of the biliary tree and has more aggressive biology and distinct genetic abnormalities. According to the practice guidelines for iCCA from the Liver Cancer Study Group of Japan and the National Comprehensive Cancer Network, upfront surgery is recommended for iCCA without distant metastasis regardless of the morphological subtype, based on clinical experience. In consideration of the biological heterogeneity of iCCA, the treatment strategy for iCCA needs to be reconsidered based on the WHO subtypes.

HNF6 and HNF4α expression in adenocarcinomas of the liver, pancreaticobiliary tract, and gastrointestinal tract: an immunohistochemical study of 480 adenocarcinomas of the digestive system

Hepatocyte nuclear factors (HNF) 6 and 4α are master transcriptional regulators of development and maintenance of the liver and pancreaticobiliary tract in mice and humans. However, little is known about the prevalence of HNF6 and HNF4α expression in carcinomas of the hepatobiliary tract and pancreas. We aimed to reveal the diagnostic utility of HNF6 and HNF4α immunolabelling in adenocarcinomas of these organs. We investigated HNF6 and HNF4α expression by immunohistochemistry using a total of 480 adenocarcinomas of the digestive system, including 282 of the hepatobiliary tract and pancreas and 198 of the gastrointestinal tract. HNF6 expression was primarily restricted to intrahepatic cholangiocarcinomas (CCs) (63%, n=80) and gallbladder adenocarcinomas (43%, n=88), among others. Notably, small duct intrahepatic CCs almost invariably expressed HNF6 (90%, n=42), showing stark contrast to a low prevalence in large duct intrahepatic CCs (10%, n=21; p<0.0001). HNF6 expression was infrequent in extrahepatic CCs (9%, n=55) and pancreatic ductal adenocarcinomas (7%, n=58), and it was rare in adenocarcinomas of the gastrointestinal tract [oesophagus/oesophagogastric junction (EGJ) (2%, n=45), stomach (2%, n=86), duodenum (0%, n=25), and colorectum (0%, n=42)]. In contrast, HNF4α was widely expressed among adenocarcinomas of the digestive system, including intrahepatic CCs (88%), extrahepatic CCs (94%), adenocarcinomas of the gallbladder (98%), pancreas (98%), oesophagus/EGJ (96%), stomach (98%), duodenum (80%), and colorectum (100%). HNF6 was frequently expressed in and almost restricted to intrahepatic CCs of small duct type and gallbladder adenocarcinomas, while HNF4α was expressed throughout adenocarcinomas of the digestive system. HNF6 immunolabelling may be useful in distinguishing small duct intrahepatic CCs from other types of CC as well as metastatic gastrointestinal adenocarcinomas.

Histopathological growth pattern and vessel co-option in intrahepatic cholangiocarcinoma

Intrahepatic cholangiocarcinoma (iCCA) exhibits different blood imaging features and prognosis depending on histology. To clarity histopathological growth patterns (HGPs) and vascularization processes of iCCA, we collected 145 surgical specimens and histologically classified them into large bile duct (LBD) (20 cases), small bile duct (SBD) (54), cholangiolocarcinoma (CLC) (35), combined SBD-CLC (cSBD-CLC) (26), and ductal plate malformation (DPM) (10) (sub)types. According to the invasive pattern at the interface between tumor and adjacent background liver, HGPs were classified into desmoplastic, pushing, and replacing HGPs. Desmoplastic HGP predominated in LBD type (55.5%), while replacing HGP was common in CLC (82.9%) and cSBD-CLC (84.6%) subtypes. Desmoplastic HGP reflected angiogenesis, while replacing HGP showed vessel co-option in addition to angiogenesis. By evaluating microvessel density (MVD) using vascular markers, ELTD1 identified vessel co-option and angiogenesis, and ELTD1-positive MVD at invasive margin in replacing HGP was significantly higher than those in desmoplastic and pushing HGPs. REDD1, an angiogenesis-related marker, demonstrated preferably higher MVD in the tumor center than in other areas. iCCA (sub)types and HGPs were closely related to vessel co-option and immune-related factors (lymphatic vessels, lymphocytes, and neutrophils). In conclusion, HGPs and vascular mechanisms characterize iCCA (sub)types and vessel co-option linked to the immune microenvironment.

Integrative analysis reveals different feature of intrahepatic cholangiocarcinoma subtypes

BACKGROUND & AIMS

Intrahepatic cholangiocarcinoma (iCCA) has two main histological subtypes: large and small duct-type iCCA, which are characterized by different clinicopathological features. This study was conducted with the purpose of expanding our understanding of their differences in molecular features and immune microenvironment.

METHODS

We selected 132 patients who underwent radical surgery at our department between 2015 and 2021 for clinical and survival analyses. Whole-exome sequencing was performed to analyse mutational landscapes. Bulk RNA sequencing and single-cell RNA sequencing data were used for pathway enrichment and immune infiltration analyses based on differentially expressed genes. The function of PPP1R1B was analysed both in vitro and in vivo and the gene mechanism was further investigated.

RESULTS

We found that large duct-type iCCA had worse overall survival and recurrence-free survival rates than small duct-type iCCA. Mutations in ARID1A, DOT1L and ELF3 usually occur in large duct-type iCCA, whereas mutations in IDH1 and BAP1 occur in small duct-type iCCA. Among the differentially expressed genes, we found that PPP1R1B was highly expressed in large duct-type iCCA tumour tissues. Expression of PPP1R1B promoted cell proliferation, migration and invasion and indicated a worse prognosis. A combination of USF2 with the promoter of PPP1R1B can enhance gene expression in iCCA, which may further affect the expression of genes such as AHNAK, C4BPA and activating the PI3K/AKT pathway.

CONCLUSIONS

Our findings extend our understanding of large and small duct-type iCCA. In addition, PPP1R1B may serve as a potential marker and therapeutic target for large duct-type iCCA.

Generation of a biliary tract cancer cell line atlas reveals molecular subtypes and therapeutic targets

Biliary tract cancers (BTCs) are a group of deadly malignancies encompassing intrahepatic and extrahepatic cholangiocarcinoma, gallbladder carcinoma, and ampullary carcinoma. Here, we present the integrative analysis of 63 BTC cell lines via multi-omics clustering and genome- scale CRISPR screens, providing a platform to illuminate BTC biology and inform therapeutic development. We identify dependencies broadly enriched in BTC compared to other cancers as well as dependencies selective to the anatomic subtypes. Notably, cholangiocarcinoma cell lines are stratified into distinct lineage subtypes based on biliary or dual biliary/hepatocyte marker signatures, associated with dependency on specific lineage survival factors. Transcriptional analysis of patient specimens demonstrates the prognostic significance of these lineage subtypes. Additionally, we delineate strategies to enhance targeted therapies or to overcome resistance in cell lines with key driver gene mutations. Furthermore, clustering based on dependencies and proteomics data elucidates unexpected functional relationships, including a BTC subgroup with partial squamous differentiation. Thus, this cell line atlas reveals potential therapeutic targets in molecularly defined BTCs, unveils biologically distinct disease subtypes, and offers a vital resource for BTC research.

Recommendations on maximising the clinical value of tissue in the management of patients with intrahepatic cholangiocarcinoma

Background & Aims

Patients with intrahepatic cholangiocarcinoma can now be managed with targeted therapies directed against specific molecular alterations. Consequently, tissue samples submitted to the pathology department must produce molecular information in addition to a diagnosis or, for resection specimens, staging information. The pathologist's role when evaluating these specimens has therefore changed to accommodate such personalised approaches.

Methods

We developed recommendations and guidance for pathologists by conducting a systematic review of existing guidance to generate candidate statements followed by an international Delphi process. Fifty-nine pathologists from 28 countries in six continents rated statements mapped to all elements of the specimen pathway from receipt in the pathology department to authorisation of the final written report. A separate survey of 'end-users' of the report including surgeons, oncologists, and gastroenterologists was undertaken to evaluate what information should be included in the written report to enable appropriate patient management.

Results

Forty-eight statements reached consensus for inclusion in the guidance including 10 statements about the content of the written report that also reached consensus by end-user participants. A reporting proforma to allow easy inclusion of the recommended data points was developed.

Conclusions

These guiding principles and recommendations provide a framework to allow pathologists reporting on patients with intrahepatic cholangiocarcinoma to maximise the informational yield of specimens required for personalised patient management.

Impact and Implications

Biopsy or resection lesional tissue from intrahepatic cholangiocarcinoma must yield information about the molecular abnormalities within the tumour that define suitability for personalised therapies in addition to a diagnosis and staging information. Here, we have developed international consensus guidance for pathologists that report such cases using a Delphi process that sought the views of both pathologists and 'end-users of pathology reports. The guide highlights the need to report cases in a way that preserves tissue for molecular testing and emphasises that reporting requires interpretation of histological characteristics within the broader clinical and radiological context. The guide will allow pathologists to report cases of intrahepatic cholangiocarcinoma in a uniform manner that maximises the value of the tissue received to facilitate optimal multidisciplinary patient management.

Integrative genomic analyses of European intrahepatic cholangiocarcinoma: Novel ROS1 fusion gene and PBX1 as prognostic marker

BACKGROUND

Cholangiocarcinoma (CCA) is a fatal cancer of the bile duct with a poor prognosis owing to limited therapeutic options. The incidence of intrahepatic CCA (iCCA) is increasing worldwide, and its molecular basis is emerging. Environmental factors may contribute to regional differences in the mutation spectrum of European patients with iCCA, which are underrepresented in systematic genomic and transcriptomic studies of the disease.

METHODS

We describe an integrated whole-exome sequencing and transcriptomic study of 37 iCCAs patients in Germany.

RESULTS

We observed as most frequently mutated genes ARID1A (14%), IDH1, BAP1, TP53, KRAS, and ATM in 8% of patients. We identified FGFR2::BICC1 fusions in two tumours, and FGFR2::KCTD1 and TMEM106B::ROS1 as novel fusions with potential therapeutic implications in iCCA and confirmed oncogenic properties of TMEM106B::ROS1 in vitro. Using a data integration framework, we identified PBX1 as a novel central regulatory gene in iCCA. We performed extended screening by targeted sequencing of an additional 40 CCAs. In the joint analysis, IDH1 (13%), BAP1 (10%), TP53 (9%), KRAS (7%), ARID1A (7%), NF1 (5%), and ATM (5%) were the most frequently mutated genes, and we found PBX1 to show copy gain in 20% of the tumours. According to other studies, amplifications of PBX1 tend to occur in European iCCAs in contrast to liver fluke-associated Asian iCCAs.

CONCLUSIONS

By analyzing an additional European cohort of iCCA patients, we found that PBX1 protein expression was a marker of poor prognosis. Overall, our findings provide insight into key molecular alterations in iCCA, reveal new targetable fusion genes, and suggest that PBX1 is a novel modulator of this disease.

An Immunohistochemical Analysis of Osteopontin and S100 Calcium-binding Protein P is Useful for Subclassifying Large- and Small-duct Type Intrahepatic Cholangiocarcinomas

Intrahepatic cholangiocarcinoma (iCCA) has been newly subclassified into two different subtypes: large-duct (LD) type and small-duct (SD) type. However, many cases are difficult to subclassify, and there is no consensus regarding subclassification criteria. LD type expresses the highly sensitive diagnostic marker S100 calcium-binding protein P (S100P), while SD type lacks sensitive markers. We identified osteopontin (OPN) as a highly sensitive marker for SD type. This study aimed to develop new subclassification criteria for LD-type and SD-type iCCA. We retrospectively investigated 74 patients with iCCA and subclassified them based on whole-section immunostaining of S100P and OPN. Of the 74 cases, 41 were subclassified as LD type, 32 as SD type, and one was indeterminate. Notably, all S100P-negative cases had OPN positivity. Seventy-three of the 74 cases (98.6%) were clearly and easily subclassified as LD or SD type using only these 2 markers. We also determined the value of immunohistochemistry in cases that were difficult to diagnose based on hematoxylin-eosin and Alcian blue-periodic acid-Schiff staining. Furthermore, we analyzed the clinicopathological characteristics and prognoses of these 2 subtypes. LD type was a poor prognostic factor on univariate analysis; it had significantly worse overall survival ( P = 0.007) and recurrence-free survival ( P < 0.001) than the SD type. In conclusion, we propose new subclassification criteria for iCCA based on immunostaining of S100P and OPN. These criteria may help pathologists to diagnose subtypes of iCCA, supporting future clinical trials and the development of medications for these 2 subtypes as distinct cancers.

Practical considerations for pathological diagnosis and molecular profiling of cholangiocarcinoma: an expert review for best practices

INTRODUCTION

Advances in precision medicine have expanded access to targeted therapies and demand for molecular profiling of cholangiocarcinoma (CCA) patients in routine clinical practice. However, pathologists face challenges in establishing a definitive intrahepatic CCA (iCCA) diagnosis while preserving sufficient tissue for molecular profiling. Additionally, they frequently face challenges in optimal tissue handling to preserve nucleic acid integrity.

AREAS COVERED

This article first identifies the challenges in establishing a definitive diagnosis of iCCA in a lesional liver biopsy while preserving sufficient tissue for molecular profiling. Then, the authors explore the clinical value of molecular profiling, the basic principles of single gene and next-generation sequencing (NGS) techniques, and the challenges in tissue sampling for genomic testing. They also propose an algorithm for best practice in tissue management for molecular profiling of CCA.

EXPERT OPINION

Several practical challenges face pathologists during tissue sampling and processing for molecular profiling. Optimized tissue processing, careful tissue handling, and selection of appropriate approaches to molecular testing are essential to ensure that the highest possible quality of diagnostic information is provided in the greatest proportion of cases.

Recent Advances in Pathology of Intrahepatic Cholangiocarcinoma

Intrahepatic cholangiocarcinoma (ICCA) is a malignant epithelial neoplasm characterized by biliary differentiation within the liver. ICCA is molecularly heterogeneous and exhibits a broad spectrum of histopathological features. It is a highly aggressive carcinoma with high mortality and poor survival rates. ICCAs are classified into two main subtypes: the small-duct type and large-duct types. These two tumor types have different cell origins and clinicopathological features. ICCAs are characterized by numerous molecular alterations, including mutations in KRAS, TP53, IDH1/2, ARID1A, BAP1, BRAF, SAMD4, and EGFR, and FGFR2 fusion. Two main molecular subtypes-inflammation and proliferation-have been proposed. Recent advances in high-throughput assays using next-generation sequencing have improved our understanding of ICCA pathogenesis and molecular genetics. The diagnosis of ICCA poses a significant challenge for pathologists because of its varied morphologies and phenotypes. Accurate diagnosis of ICCA is essential for effective patient management and prognostic determination. This article provides an updated overview of ICCA pathology, focusing particularly on molecular features, histological subtypes, and diagnostic approaches.

Impact of Tumor Subclassifications for Identifying an Appropriate Surgical Strategy in Patients with Intrahepatic Cholangiocarcinoma

BACKGROUND

Intrahepatic cholangiocarcinoma (ICC) is subclassified into small and large duct types. The impact of these subclassifications for identifying appropriate surgical strategies remains unclear.

PATIENTS AND METHODS

This study included 118 patients with ICC who underwent liver resection. Based on the pathological examination results, the participants were divided into the small duct-type ICC group (n = 64) and large duct-type ICC group (n = 54). The clinicopathological features and postoperative outcomes were compared between the two groups to investigate the impact of subclassification for selecting appropriate surgical strategies.

RESULTS

Ten patients in the small duct-type ICC group had synchronous or metachronous hepatocellular carcinoma. The large duct-type ICC group had higher proportions of patients who underwent major hepatectomy, extrahepatic bile duct resection, portal vein resection, and lymph node sampling or dissection than the small duct-type ICC group. The large duct-type ICC group had significantly higher incidences of lymph node metastasis/recurrence and pathological major vessel invasion than the other. The small duct-type ICC group exhibited significantly higher recurrence-free and overall survival rates than the large duct-type ICC group. Further, the large duct-type ICC group had a significantly higher incidence of lymph node metastasis/recurrence than the small duct-type ICC at the perihilar region group.

CONCLUSIONS

Suitable surgical strategies may differ between the small and large duct-type ICCs. In patients with large duct-type ICCs, hepatectomy with lymph node dissection and/or biliary reconstruction should be considered, whereas hepatectomy without these advanced procedures can be suggested for patients with small duct-type ICCs.

Intrahepatic cholangiocarcinoma: Evolving strategies in management and treatment

Intrahepatic cholangiocarcinoma is the second most frequent primary liver cancer after hepatocellular carcinoma. According to International Classification of Diseases-11 (ICD-11), intrahepatic cholangiocarcinoma is identified by a specific diagnostic code, different with respect to perihilar-CCA or distal-CCA. Intrahepatic cholangiocarcinoma originates from intrahepatic small or large bile ducts including the second-order bile ducts and has a silent presentation that combined with the highly aggressive nature and refractoriness to chemotherapy contributes to the alarming increasing incidence and mortality. Indeed, at the moment of the diagnosis, less than 40% of intrahepatic cholangiocarcinoma are suitable of curative surgical therapy, that is so far the only effective treatment. The main goals of clinicians and researchers are to make an early diagnosis, and to carry out molecular characterization to provide the patient with personalized treatment. Unfortunately, these goals are not easily achievable because of the heterogeneity of this tumor from anatomical, molecular, biological, and clinical perspectives. However, recent progress has been made in molecular characterization, surgical treatment, and management of intrahepatic cholangiocarcinoma and, this article deals with these advances.

Enteroblastic cholangiocarcinoma: An uncommon, underrecognized subtype of bile duct cancer

Enteroblastic carcinoma is clinically characterized by an elevated serum level of alpha-fetoprotein (AFP) and is histologically characterized by cancer cells with a clear cytoplasm and 'blastic' coarse chromatin. It sometimes has an element of hepatoid carcinoma; therefore, these two neoplasms are often regarded as sister entities. Although hepatoid carcinoma in the biliary tree has been reported, enteroblastic cholangiocarcinoma is extremely uncommon. In the present study, four cases of enteroblastic cholangiocarcinoma were examined. Tumors were located inside the liver (n = 2) or common bile duct (n = 2). The two intrahepatic cases had a history of primary sclerosing cholangitis, and serum AFP levels were elevated in both. One unresectable case was diagnosed by needle liver biopsy, while the remaining three underwent surgical resection. Histologically, all cases showed similar microscopic features. Cuboidal or polygonal cancer cells with the characteristic clear cytoplasm and subnuclear vacuoles were arranged in a papillary, micropapillary, tubular, or solid architecture. One case had an element of pancreatobiliary-type adenocarcinoma, while a hepatoid carcinoma element was not observed in any cases. All cases were positive for AFP, glypican 3, and SALL4, with SALL4 being the most widely expressed. Heppar-1 and arginase-1 were negative, except for one case, which was positive for Heppar-1. In conclusion, enteroblastic cholangiocarcinoma is an uncommon subtype of biliary tract malignancy. These cases may have been categorized as 'clear cell' cholangiocarcinoma. Although enteroblastic cholangiocarcinoma seems to occur more commonly in extrahepatic regions, including the gallbladder, it may also develop in the liver, particularly in patients with primary sclerosing cholangitis.

Expert Consensus on Pathological Diagnosis of Intrahepatic Cholangiocarcinoma (2022 version)

Intrahepatic cholangiocarcinoma (iCCA) can originate from the large bile duct group (segment bile ducts and area bile ducts), small bile duct group (septal bile ducts and interlobular bile ducts), and terminal bile duct group (bile ductules and canals of Hering) of the intrahepatic biliary tree, which can be histopathological corresponding to large duct type iCCA, small duct type iCCA and iCCA with ductal plate malformation pattern, and cholangiolocarcinoma, respectively. The challenge in pathological diagnosis of above subtypes of iCCA falls in the distinction of cellular morphologies, tissue structures, growth patterns, invasive behaviors, immunophenotypes, molecular mutations, and surgical prognoses. For these reasons, this expert consensus provides nine recommendations as a reference for standardizing and refining the diagnosis of pathological subtypes of iCCA, mainly based on the 5th edition of the World Health Organization Classification of Tumours of the Digestive System.

British Society of Gastroenterology guidelines for the diagnosis and management of cholangiocarcinoma

These guidelines for the diagnosis and management of cholangiocarcinoma (CCA) were commissioned by the British Society of Gastroenterology liver section. The guideline writing committee included a multidisciplinary team of experts from various specialties involved in the management of CCA, as well as patient/public representatives from AMMF (the Cholangiocarcinoma Charity) and PSC Support. Quality of evidence is presented using the Appraisal of Guidelines for Research and Evaluation (AGREE II) format. The recommendations arising are to be used as guidance rather than as a strict protocol-based reference, as the management of patients with CCA is often complex and always requires individual patient-centred considerations.

Role of immunophenotypic characterisation in prognostic subtyping of intrahepatic cholangiocarcinoma

Intrahepatic cholangiocarcinoma (iCCA) is classified by the 5th WHO classification of tumours of the digestive system as large duct type (LDT) and small duct type (SDT), based on the anatomical location, morphological appearances, immunophenotype, and gene events. We evaluated the subtyping system using real-world data and established a supplementary method using immunohistochemical (IHC) detection. We retrospectively investigated 190 cases of surgically resected iCCA and classified them according to histological evaluations and gene detection. The prognostic value of the IHC markers were evaluated according to the relapse-free survival (RFS) and overall survival (OS). Basic histological classification was insufficient, with 61 cases classified as uncertain. This method showed no prognostic value for RFS or OS. The four-marker IHC detection, including EMA, S100P, N-cadherin, and CRP, which classified 68 cases as LDT, 108 cases as SDT, and 14 cases as uncertain, was highly efficient in subtyping and prognosis. The seven-marker method, including CD56, MUC5AC and MUC6, was consistent with the four-marker method. FGFR2 gene fusion was exclusively detected in 20 cases of SDT iCCA, according to the four- and seven-marker IHC detection. This novel method of iCCA classification exhibited diagnostic, prognostic and therapeutic value in clinical practice.

Challenges in Diagnosing and Reporting Cholangiocarcinoma

Intrahepatic cholangiocarcinoma is a challenge to the practicing surgical pathologist for several reasons. It is rare in many parts of the world, and thus practical exposure may be limited. Related to the fact of its rarity is the fact that more common tumors which frequently metastasize to the liver can be morphologically indistinguishable (eg, pancreatic ductal adenocarcinoma). Immunohistochemical testing is generally non-contributory in this context. Other difficulties arise from the protean morphologic manifestations of cholangiocarcinoma (ie, small duct vs. large duct) and the existence of combined cholangiocarcinoma and hepatocellular carcinoma. These, and other issues of concern to the practicing diagnostic pathologist are discussed herein.

Novel insights into the intraepithelial spread of extrahepatic cholangiocarcinoma: clinicopathological study of 382 cases on extrahepatic cholangiocarcinoma

Background

Extrahepatic cholangiocarcinoma (eCCA) is a rare and aggressive disease and consisted of conventional eCCA and intraductal papillary neoplasm of the bile duct (IPNB). Intraepithelial spread (IES) of cancer cells beyond the invasive area is often observed in IPNBs; however, the prevalence of IES remains to be examined in conventional eCCAs. Here, we evaluated the clinicopathological features of eCCAs according to tumor location, with a focus on the presence of IES. The IES extension was also compared among biliary tract cancers (BTCs).

Methods

We examined the prevalence and clinicopathological significance of IES in eCCAs (n=382) and the IES extension of BTCs, including gallbladder (n=172), cystic duct (n=20), and ampullary cancers (n=102).

Results

Among the invasive eCCAs, IPNB had a higher rate of IES (89.2%) than conventional eCCAs (57.0%). Among conventional eCCAs, distal eCCAs (75.4%) had a significantly higher prevalence of IES than perihilar eCCAs (41.3%). The presence of IES was associated with a significantly higher survival rate in patients with distal eCCAs (P=0.030). Extension of the IES into the cystic duct (CyD) in distal eCCAs that cancer cells reached the junction of the CyD was a favorable prognostic factor (P<0.001). The association of survival with IES, either on the extrahepatic bile duct or on the CyD, differed depending on the tumor location and type of eCCA. The extension properties of IES were also dependent on different types of tumors among BTCs; usually, the IES incidence became higher than 50% in the tissues that the tumor developed, whereas IES extension to other tissues decreased the incidence.

Conclusion

Thus, eCCAs have different clinicopathological characteristics depending on the tumor location and type.

A preoperative scoring system to predict lymph node metastasis in intrahepatic cholangiocarcinoma

BACKGROUND

The abnormality of imaging finding of lymph node (LN) has demonstrated unsatisfactory diagnostic accuracy for pathologic lymph node metastasis (LNM). We aimed to develop and validate a simple scoring system predicting LNM in patients with intrahepatic cholangiocarcinoma (iCCA) prior to surgery based on MRI and clinical findings.

METHODS

We retrospectively enrolled consecutive patients who underwent surgical resection for treatment-naïve iCCA from six institutions between January 2009 and December 2015. Patients who underwent lymph node dissection (LND) were randomly assigned to the training and validation cohorts at a 2:1 ratio, an¹ìd pathologic LN status was evaluated. Patients who did not undergo LND were assigned to the test cohort, and clinical LN status was evaluated. Using MRI and clinical findings, a preoperative LNM score was developed in the training cohort and validated in the validation and test cohorts.

RESULTS

The training, validation, and test cohorts included 102, 53, and 118 patients, respectively. The preoperative LNM score consisted of serum carcinoembryonic antigen and two MRI findings (suspicious LN and bile duct invasion). The preoperative LNM score was associated with pathologic LNM in training (p < 0.001) and validation (p = 0.010) cohorts and clinical LNM in test cohort (p < 0.001). The preoperative LNM score outperformed MRI-suspicious LN alone in predicting pathologic LNM (area under the curve, 0.703 vs. 0.604, p = 0.004). The preoperative LNM score was also associated with overall survival in all cohorts (p < 0.001).

CONCLUSIONS

Our preoperative LNM score was significantly associated with pathologic or clinical LNM and outperformed MRI-suspicious LN alone.

EASL-ILCA Clinical Practice Guidelines on the management of intrahepatic cholangiocarcinoma

Intrahepatic cholangiocarcinoma (iCCA) develops inside the liver, between bile ductules and the second-order bile ducts. It is the second most frequent primary liver cancer after hepatocellular carcinoma, and its global incidence is increasing. It is associated with an alarming mortality rate owing to its silent presentation (often leading to late diagnosis), highly aggressive nature and resistance to treatment. Early diagnosis, molecular characterisation, accurate staging and personalised multidisciplinary treatments represent current challenges for researchers and physicians. Unfortunately, these challenges are beset by the high heterogeneity of iCCA at the clinical, genomic, epigenetic and molecular levels, very often precluding successful management. Nonetheless, in the last few years, progress has been made in molecular characterisation, surgical management, and targeted therapy. Recent advances together with the awareness that iCCA represents a distinct entity amongst the CCA family, led the ILCA and EASL governing boards to commission international experts to draft dedicated evidence-based guidelines for physicians involved in the diagnostic, prognostic, and therapeutic management of iCCA.

DNA methylation-based classifier differentiates intrahepatic pancreato-biliary tumours

BACKGROUND

Differentiating intrahepatic cholangiocarcinomas (iCCA) from hepatic metastases of pancreatic ductal adenocarcinoma (PAAD) is challenging. Both tumours have similar morphological and immunohistochemical pattern and share multiple driver mutations. We hypothesised that DNA methylation-based machine-learning algorithms may help perform this task.

METHODS

We assembled genome-wide DNA methylation data for iCCA (n = 259), PAAD (n = 431), and normal bile duct (n = 70) from publicly available sources. We split this cohort into a reference (n = 399) and a validation set (n = 361). Using the reference cohort, we trained three machine learning models to differentiate between these entities. Furthermore, we validated the classifiers on the technical validation set and used an internal cohort (n = 72) to test our classifier.

FINDINGS

On the validation cohort, the neural network, support vector machine, and the random forest classifiers reached accuracies of 97.68%, 95.62%, and 96.5%, respectively. Filtering by anomaly detection and thresholds improved the accuracy to 99.07% (37 samples excluded by filtering), 96.22% (17 samples excluded), and 100% (44 samples excluded) for the neural network, support vector machine and random forest, respectively. Because of best balance between accuracy and number of predictable cases we tested the neural network with applied filters on the in-house cohort, obtaining an accuracy of 95.45%.

INTERPRETATION

We developed a classifier that can differentiate between iCCAs, intrahepatic metastases of a PAAD, and normal bile duct tissue with high accuracy. This tool can be used for improving the diagnosis of pancreato-biliary cancers of the liver.

FUNDING

This work was supported by Berlin Institute of Health (JCS Program), DKTK Berlin (Young Investigator Grant 2022), German Research Foundation (493697503 and 314905040 - SFB/TRR 209 Liver Cancer B01), and German Cancer Aid (70113922).

Onco-Pathogen Mediated Cancer Progression and Associated Signaling Pathways in Cancer Development

Infection with viruses, bacteria, and parasites are thought to be the underlying cause of about 8-17% of the world's cancer burden, i.e., approximately one in every five malignancies globally is caused by an infectious pathogen. Oncogenesis is thought to be aided by eleven major pathogens. It is crucial to identify microorganisms that potentially act as human carcinogens and to understand how exposure to such pathogens occur as well as the following carcinogenic pathways they induce. Gaining knowledge in this field will give important suggestions for effective pathogen-driven cancer care, control, and, ultimately, prevention. This review will mainly focus on the major onco-pathogens and the types of cancer caused by them. It will also discuss the major pathways which, when altered, lead to the progression of these cancers.

Unraveling the heterogeneity of cholangiocarcinoma and identifying biomarkers and therapeutic strategies with single-cell sequencing technology

Cholangiocarcinoma (CCA) is a common malignant tumor of the biliary tract that carries a high burden of morbidity and a poor prognosis. Due to the lack of precise diagnostic methods, many patients are often diagnosed at advanced stages of the disease. The current treatment options available are of varying efficacy, underscoring the urgency for the discovery of more effective biomarkers for early diagnosis and improved treatment. Recently, single-cell sequencing (SCS) technology has gained popularity in cancer research. This technology has the ability to analyze tumor tissues at the single-cell level, thus providing insights into the genomics and epigenetics of tumor cells. It also serves as a practical approach to study the mechanisms of cancer progression and to explore therapeutic strategies. In this review, we aim to assess the heterogeneity of CCA using single-cell sequencing technology, with the ultimate goal of identifying possible biomarkers and potential treatment targets.

SULT1A1-dependent sulfonation of alkylators is a lineage-dependent vulnerability of liver cancers

Adult liver malignancies, including intrahepatic cholangiocarcinoma and hepatocellular carcinoma, are the second leading cause of cancer-related deaths worldwide. Most individuals are treated with either combination chemotherapy or immunotherapy, respectively, without specific biomarkers for selection. Here using high-throughput screens, proteomics and in vitro resistance models, we identify the small molecule YC-1 as selectively active against a defined subset of cell lines derived from both liver cancer types. We demonstrate that selectivity is determined by expression of the liver-resident cytosolic sulfotransferase enzyme SULT1A1, which sulfonates YC-1. Sulfonation stimulates covalent binding of YC-1 to lysine residues in protein targets, enriching for RNA-binding factors. Computational analysis defined a wider group of structurally related SULT1A1-activated small molecules with distinct target profiles, which together constitute an untapped small-molecule class. These studies provide a foundation for preclinical development of these agents and point to the broader potential of exploiting SULT1A1 activity for selective targeting strategies.

Preoperative subcategorization based on magnetic resonance imaging in intrahepatic cholangiocarcinoma

BACKGROUND

Appropriate preoperative identification of iCCA subtype is essential for personalized management, so the aim of this study is to investigate the role of MR imaging features in preoperatively differentiating the iCCA subtype.

METHODS

Ninety-three patients with mass-forming intrahepatic cholangiocarcinoma (iCCA, 63 small duct type and 30 large duct type) were retrospectively enrolled according to the latest 5th WHO classification (mean age, males vs. females: 60.66 ± 10.53 vs. 61.88 ± 12.82, 50 men). Significant imaging features for differentiating large duct iCCA and small duct iCCA were identified using univariate and multivariate logistic regression analyses, and a regression-based predictive model was then generated. Furthermore, diagnostic performance parameters of single significant imaging features and the predictive model were obtained, and corresponding receiver operating characteristic (ROC) curves were subsequently presented.

RESULTS

The univariate analysis showed that tumor in vein, arterial phase hypoenhancement, intrahepatic duct dilatation, lack of targetoid restriction and lack of targetoid appearance in T2 were predictors of large duct type iCCA. Arterial phase hypoenhancement, intrahepatic duct dilatation and lack of targetoid restriction were independent predictors for large duct type iCCA in multivariate analysis. The regression-based predictive model has achieved the best preoperative prediction performance in iCCA subcategorization so far. The area under the ROC curve of the regression-based predictive model was up to 0.91 (95% CI: 0.85, 0.98), and it was significantly higher than every single significant imaging feature.

CONCLUSIONS

Arterial phase hypoenhancement, intrahepatic duct dilatation and lack of targetoid restriction could be considered reliable MR imaging indicators of large duct type iCCA. MR imaging features can facilitate noninvasive prediction of iCCA subtype with satisfactory predictive performance.

Intrahepatic cholangiocarcinoma: typical features, uncommon variants, and controversial related entities

Pathologists play a central role in the diagnosis and classification of intrahepatic cholangiocarcinoma (iCCA). iCCA is currently classified into small- and large-duct types. Small-duct iCCA is characterized by a mass-forming gross appearance, mucus-poor ductule-like histology, and frequent association with chronic parenchymal liver diseases (eg, cirrhosis). Large-duct iCCA is an infiltrative duct-forming adenocarcinoma with a fibrotic stroma, similar to perihilar cholangiocarcinoma. Chronic cholangiopathies (eg, primary sclerosing cholangitis, liver flukes) are associated with an increased risk of large-duct iCCA. Alterations in IDH1/2, BAP1, or FGFR2 are characteristic molecular features of small-duct iCCA, whereas mutations in KRAS and SMAD4 and the amplification of MDM2 are mainly observed in large-duct iCCA. C-reactive protein and N-cadherin are commonly expressed in small-duct iCCA, and S100P is a good marker for large-duct iCCA. In addition to well-known subtypes (eg, cholangiolocellular carcinoma), uncommon variants are recognized. A tubulocystic variant is often misinterpreted as a benign neoplasm. Mucoepidermoid and enteroblastic variants are under-recognized and pose a diagnostic challenge. Cholangioblastic cholangiocarcinoma characterized by inhibin-A expression was recently found to have an NIPBL-NACC1 gene fusion. Despite significant advances in hepatobiliary pathology, there are still controversial premalignant entities that require large comprehensive studies. There are morphological overlaps between biliary adenofibroma and the tubulocystic variant of iCCA. Type 2 intraductal papillary neoplasm of the bile duct (IPNB) is typically associated with invasive malignancy at the initial presentation and lacks unique molecular features. Therefore, some pathologists prefer the term "papillary cholangiocarcinoma" over type 2 IPNB.

Risk Assessment and Cholangiocarcinoma: Diagnostic Management and Artificial Intelligence

Intrahepatic cholangiocarcinoma (iCCA) is the second most common primary liver tumor, with a median survival of only 13 months. Surgical resection remains the only curative therapy; however, at first detection, only one-third of patients are at an early enough stage for this approach to be effective, thus rendering early diagnosis as an efficient approach to improving survival. Therefore, the identification of higher-risk patients, whose risk is correlated with genetic and pre-cancerous conditions, and the employment of non-invasive-screening modalities would be appropriate. For several at-risk patients, such as those suffering from primary sclerosing cholangitis or fibropolycystic liver disease, the use of periodic (6-12 months) imaging of the liver by ultrasound (US), magnetic Resonance Imaging (MRI)/cholangiopancreatography (MRCP), or computed tomography (CT) in association with serum CA19-9 measurement has been proposed. For liver cirrhosis patients, it has been proposed that at-risk iCCA patients are monitored in a similar fashion to at-risk HCC patients. The possibility of using Artificial Intelligence models to evaluate higher-risk patients could favor the diagnosis of these entities, although more data are needed to support the practical utility of these applications in the field of screening. For these reasons, it would be appropriate to develop screening programs in the research protocols setting. In fact, the success of these programs reauires patient compliance and multidisciplinary cooperation.

Integrative analysis of multiple genomic data from intrahepatic cholangiocarcinoma organoids enables tumor subtyping

As genomic analysis technology has advanced, it has become possible to sub-classify intrahepatic cholangiocarcinoma (ICC) at the histological or molecular level. Here, we verify the recently suggested two subgroups of ICC in the organoids model, compare the characteristics between types. ICC patients are subclassified into small-duct (SD) and large-duct (LD) subtype according to histological characteristics. ICC organoids are established, and unsupervised principal component analysis clustering separates each type of ICC. Differential gene expression reveals enrichment on KRAS, TGFβ and ERBB2 signaling pathways in LD-type compared with SD-type (P < 0.05). Gene set enrichment analysis demonstrates that the cholangiocarcinoma class 2 signature, defined by Andersen et al., is enriched in the LD-type (enrichment Score = 2.19, P < 0.001). A protein-protein interaction network analysis identifies ZNF217 as a significant hub protein (odds ratio = 4.96, P = 0.0105). We perform prospective modeling of histological subtype using patient-derived organoids. Moreover, gene expression profiling of ICC organoids enables identification of type-specific targetable pathways.

Pathology of Combined Hepatocellular Carcinoma-Cholangiocarcinoma: An Update

Combined hepatocellular carcinoma-cholangiocarcinoma (cHCC-CCA) is a rare primary liver cancer that is composed of both hepatocellular and cholangiocellular differentiated cells. It is slightly more common in men and among Asian and Pacific islanders. Overall, risk factors are similar to classic risk factors of hepatocellular carcinoma (HCC). The classification has significantly evolved over time. The last WHO classification (2019) mainly emphasized diagnosis on morphological basis with routine stainings, discarded previously recognized classifications with carcinomas with stem cell features, introduced intermediate cell carcinoma as a specific subtype and considered cholangiolocarcinoma as a subtype of cholangiocellular carcinoma. Immunohistochemical markers may be applied for further specification but have limited value for diagnosis. Recent discoveries in molecular pathway regulation may pioneer new therapeutic approaches for this poor prognostic and challenging diagnosis.

Understanding the Clinical Significance of MUC5AC in Biliary Tract Cancers

Biliary tract cancers (BTC) arise from biliary epithelium and include cholangiocarcinomas or CCA (including intrahepatic (ICC) and extrahepatic (ECC)) and gallbladder cancers (GBC). They often have poor outcomes owing to limited treatment options, advanced presentations, frequent recurrence, and poor response to available systemic therapy. Mucin 5AC (MUC5AC) is rarely expressed in normal biliary epithelium, but can be upregulated in tissues of benign biliary disease, premalignant conditions (e.g., biliary intraepithelial neoplasia), and BTCs. This mucin's numerous glycoforms can be divided into less-glycosylated immature and heavily-glycosylated mature forms. Reported MUC5AC tissue expression in BTC varies widely, with some associations based on cancer location (e.g., perihilar vs. peripheral ICC). Study methods were variable regarding cancer subtypes, expression positivity thresholds, and MUC5AC glycoforms. MUC5AC can be detected in serum of BTC patients at high concentrations. The hesitancy in developing MUC5AC into a clinically useful biomarker in BTC management is due to variable evidence on the diagnostic and prognostic value. Concrete conclusions on tissue MUC5AC are difficult, but serum detection might be relevant for diagnosis and is associated with poor prognosis. Future studies are needed to further the understanding of the potential clinical value of MUC5AC in BTC, especially regarding predictive and therapeutic value.

Cholangiocarcinoma: Molecular Abnormalities and Cells of Origin

Cholangiocarcinomas (CCAs) are a group of heterogeneous epithelial malignancies that can originate at the level of any location of the biliary tree. These tumors are relatively rare but associated with a high rate of mortality. CCAs are morphologically and molecularly heterogeneous and for their location can be distinguished as intracellular and extracellular, subdivided into perihilar and distal. Recent epidemiological, molecular, and cellular studies have supported that the consistent heterogeneity observed for CCAs may result from the convergence of various key elements mainly represented by risk factors, heterogeneity of the associated molecular abnormalities at genetic and epigenetic levels and by different potential cells of origin. These studies have consistently contributed to better defining the pathogenesis of CCAs and to identify in some instances new therapeutic targets. Although the therapeutic progress were still limited, these observations suggest that a better understanding of the molecular mechanisms underlying CCA in the future will help to develop more efficacious treatment strategies.

KRAS mutation in intrahepatic cholangiocarcinoma: Linkage with metastasis-free survival and reduced E-cadherin expression

BACKGROUND AND AIMS

Although KRAS mutations are the major driver of intrahepatic cholangiocarcinoma (ICC), their role remains unexplored. This study aimed to elucidate the prognostic effects, association with clinicopathologic characteristics and potent functions of KRAS mutations in ICC.

METHODS

A hundred and seven resected stage I-III ICCs were analysed for KRAS mutation status and its link with clinicopathological features. An independent validation cohort (n = 138) was included. In vitro analyses using KRAS-mutant ICC cell lines were performed.

RESULTS

KRAS mutation was significantly associated with worse overall survival in stage I-III ICCs, which was validated in an independent cohort. Recurrence-free survival did not significantly differ between cases with and without KRAS mutations, but if limited to recurrence with extrahepatic metastasis, KRAS-mutant cases showed significantly worse distant metastasis-free survival than KRAS-wild cases showed. KRAS mutations were associated with frequent tumour budding with reduced E-cadherin expression. In vitro, KRAS depletion caused marked inhibition of cell growth and migration together with E-cadherin upregulation in KRAS-mutant ICC cells. The RNA-sequencing assay revealed that KRAS depletion caused MYC pathway downregulation and interferon pathway upregulation.

CONCLUSIONS

Our observations suggest that KRAS mutations are associated with aggressive behaviour of ICC, especially the development of extrahepatic metastasis. Mutant KRAS is likely to change the adhesive status of ICC cells, affect the responsiveness of tumour cells to interferon immune signals, and consequently promote extrahepatic metastasis. KRAS mutation status, which predicts the prognoses of patients with ICC after surgical resection, is expected to help stratify patients better for individual postoperative treatment strategies.

Clinical relevance of biomarkers in cholangiocarcinoma: critical revision and future directions

Cholangiocarcinoma (CCA) is a malignant tumour arising from the biliary system. In Europe, this tumour frequently presents as a sporadic cancer in patients without defined risk factors and is usually diagnosed at advanced stages with a consequent poor prognosis. Therefore, the identification of biomarkers represents an utmost need for patients with CCA. Numerous studies proposed a wide spectrum of biomarkers at tissue and molecular levels. With the present paper, a multidisciplinary group of experts within the European Network for the Study of Cholangiocarcinoma discusses the clinical role of tissue biomarkers and provides a selection based on their current relevance and potential applications in the framework of CCA. Recent advances are proposed by dividing biomarkers based on their potential role in diagnosis, prognosis and therapy response. Limitations of current biomarkers are also identified, together with specific promising areas (ie, artificial intelligence, patient-derived organoids, targeted therapy) where research should be focused to develop future biomarkers.

Integrative Analysis of Intrahepatic Cholangiocarcinoma Subtypes for Improved Patient Stratification: Clinical, Pathological, and Radiological Considerations

Simple Summary

Liver cancer subtypes differ in prognosis and genetic alterations. An accurate diagnosis made on time is the key aspect of clinical decision-making. Hence, a correct diagnosis is of pivotal importance for individual patients. In this study, we identified the most relevant clinical, radiological, and histological parameters for an improved subtype diagnosis of intrahepatic cholangiocarcinoma. As a result of our study, the radiologist should consider factors such as growth pattern, location, and contrast agent behavior. For the pathologist, precursor lesions, mucin secretion, and a periductal-infiltrating growth are of utmost importance, while immunohistochemical analyses are essential for exclusion of extrahepatic malignancies, but have so far only value for iCCA subtype analysis in the context with other parameters.

Abstract

Intrahepatic cholangiocarcinomas (iCCAs) may be subdivided into large and small duct types that differ in etiology, molecular alterations, therapy, and prognosis. Therefore, the optimal iCCA subtyping is crucial for the best possible patient outcome. In our study, we analyzed 148 small and 84 large duct iCCAs regarding their clinical, radiological, histological, and immunohistochemical features. Only 8% of small duct iCCAs, but 27% of large duct iCCAs, presented with initial jaundice. Ductal tumor growth pattern and biliary obstruction were significant radiological findings in 33% and 48% of large duct iCCAs, respectively. Biliary epithelial neoplasia and intraductal papillary neoplasms of the bile duct were detected exclusively in large duct type iCCAs. Other distinctive histological features were mucin formation and periductal-infiltrating growth pattern. Immunohistochemical staining against CK20, CA19-9, EMA, CD56, N-cadherin, and CRP could help distinguish between the subtypes. To summarize, correct subtyping of iCCA requires an interplay of several factors. While the diagnosis of a precursor lesion, evidence of mucin, or a periductal-infiltrating growth pattern indicates the diagnosis of a large duct type, in their absence, several other criteria of diagnosis need to be combined.

Biology of IDH mutant cholangiocarcinoma

Isocitrate dehydrogenase 1 and 2 (IDH1 and IDH2) are the most frequently mutated metabolic genes across human cancers. These hotspot gain-of-function mutations cause the IDH enzyme to aberrantly generate high levels of the oncometabolite, R-2-hydroxyglutarate, which competitively inhibits enzymes that regulate epigenetics, DNA repair, metabolism, and other processes. Among epithelial malignancies, IDH mutations are particularly common in intrahepatic cholangiocarcinoma (iCCA). Importantly, pharmacological inhibition of mutant IDH (mIDH) 1 delays progression of mIDH1 iCCA, indicating a role for this oncogene in tumor maintenance. However, not all patients receive clinical benefit, and those who do typically show stable disease rather than significant tumor regressions. The elucidation of the oncogenic functions of mIDH is needed to inform strategies that can more effectively harness mIDH as a therapeutic target. This review will discuss the biology of mIDH iCCA, including roles of mIDH in blocking cell differentiation programs and suppressing antitumor immunity, and the potential relevance of these effects to mIDH1-targeted therapy. We also cover opportunities for synthetic lethal therapeutic interactions that harness the altered cell state provoked by mIDH1 rather than inhibiting the mutant enzyme. Finally, we highlight key outstanding questions in the biology of this fascinating and incompletely understood oncogene.

Pathological, molecular, and clinical characteristics of cholangiocarcinoma: A comprehensive review

Cholangiocarcinomas are a heterogeneous group of highly aggressive cancers that may arise anywhere within the biliary tree. There is a wide geographical variation with regards to its incidence, and risk-factor associations which may include liver fluke infection, primary sclerosing cholangitis, and hepatolithiasis amongst others. These tumours are classified into intrahepatic, perihilar and distal based on their anatomical location. Morphologically, intrahepatic cholangiocarcinomas are further sub-classified into small and large duct variants. Perihilar and distal cholangiocarcinomas are usually mucin-producing tubular adenocarcinomas. Cholangiocarcinomas develop through a multistep carcinogenesis and are preceded by dysplastic and in situ lesions. While clinical characteristics and management of these tumours have been extensively elucidated in literature, their ultra-structure and tumour biology remain relatively unknown. This review focuses on the current knowledge of pathological characteristics, molecular alterations of cholangiocarcinoma, and its precursor lesions (including biliary intraepithelial neoplasia, intraductal papillary neoplasms of the bile duct, intraductal tubulopapillary neoplasms and mucinous cystic neoplasm).

Imaging mimickers of cholangiocarcinoma: a pictorial review

Cholangiocarcinoma (CCA) is the second most common primary hepatobiliary malignancy and presents as three separate morphological subtypes; namely mass-forming, periductal-infiltrating, and intraductal-growing patterns. Each of these subtypes have distinct imaging characteristics, as well as a variety of benign and malignant mimics, making accurate diagnosis of CCA on imaging challenging. Whilst histopathological examination is required to arrive at a definitive diagnosis, it is still important for radiologists to be cognizant of these entities and provide reasonable differential diagnoses, as these potentially have a large impact on patient management. This pictorial essay illustrates the three morphological subtypes of CCA, as well as some important mimics for each subtype, that are encountered in clinical practice.

Intrahepatic cholangiocarcinoma: tumour heterogeneity and its clinical relevance

Treatment of intrahepatic cholangiocarcinoma (iCCA) is currently at a significant turning point due to the identification of isocitrate dehydrogenase (IDH) mutations and fibroblast growth factor receptor (FGFR) fusions that can be targeted with currently available therapies. Clinical trials of these targeted therapies have been promising, and the iCCA patients who may benefit from these targeted treatments can be identified by pathological examination prior to molecular investigations. This is because IDH mutations and FGFR fusions are mainly seen in the small duct type iCCA, a subtype of iCCA defined by the 5th World Health Organization classification, which can be recognized by the pathological diagnostic process. Therefore, pathology plays an important role in precision medicine for iCCA, not only in confirming the diagnosis, but also in identifying the iCCA patients who may benefit from targeted treatments. However, caution is advised with the pathological diagnosis, as iCCA shows tumour heterogeneity, making it difficult to distinguish small duct type iCCA from hepatocellular carcinoma (HCC), and combined HCC-CCA. This review focuses on the pathological/molecular features of both subtypes of iCCA (large and small duct types), as well as their diagnostic pitfalls, clinical relevance, and future perspectives.

Epigenetic upregulation of TET2 is an independent poor prognostic factor for intrahepatic cholangiocarcinoma

Mutations in IDH1/2 and the epigenetic silencing of TET2 occur in leukaemia or glioma in a mutually exclusive manner. Although intrahepatic cholangiocarcinoma (iCCA) may harbour IDH1/2 mutations, the contribution of TET2 to carcinogenesis remains unknown. In the present study, the expression and promoter methylation of TET2 were investigated in iCCA. The expression of TET2 was assessed in 52 cases of iCCA (small-duct type, n = 33; large-duct type, n = 19) by quantitative PCR, immunohistochemistry (IHC) and a sequencing-based methylation assay, and its relationships with clinicopathological features and alterations in cancer-related genes (e.g., KRAS and IDH1) were investigated. In contrast to non-neoplastic bile ducts, which were negative for TET2 on IHC, 42 cases (81%) of iCCA showed the nuclear overexpression of TET2. Based on IHC scores (area × intensity), these cases were classified as TET2-high (n = 25) and TET2-low (n = 27). The histological type, tumour size, lymph node metastasis and frequency of mutations in cancer-related genes did not significantly differ between the two groups. Overall and recurrence-free survival were significantly worse in patients with TET2-high iCCA than in those with TET2-low iCCA. A multivariate analysis identified the high expression of TET2 as an independent prognostic factor (HR = 2.94; p = 0.007). The degree of methylation at two promoter CpG sites was significantly less in TET2-high iCCA than in TET2-low iCCA or non-cancer tissue. In conclusion, in contrast to other IDH-related neoplasms, TET2 overexpression is common in iCCA of both subtypes, and its high expression, potentially induced by promoter hypomethylation, is an independent poor prognostic factor.