Helicobacter pylori testing prior to or at gastric cancer diagnosis and survival in a diverse US patient population.

BACKGROUND: Gastric cancer (GC) accounts for the greatest disparity in cancer mortality between Black and White Americans. Although clinical trials have shown that Helicobacter pylori (Hp) treatment reduces risk of GC, Hp testing and treatment is not consistently performed in the US, and may offer an opportunity to improve survival. METHODS: In a diverse retrospective cohort of 99 GC cases diagnosed at Duke University from 2002-2020 (57% Black; 43% white), we examined the association of Hp testing and treatment prior to or at cancer diagnosis with overall survival using Cox regression analyses to calculate adjusted hazards ratios (HRs) and 95% confidence intervals (CIs). RESULTS: Overall, 62% of patients were tested for Hp prior to or at GC diagnosis. Of those, 25% tested positive and were treated < 1 year prior to or at diagnosis, 15% tested positive and were treated ≥ 1 year prior to diagnosis, 6% tested positive without evidence of treatment, and 54% tested negative. Compared to never tested, Hp testing and treatment < 1 year prior to or at diagnosis was associated with a significantly reduced likelihood of death (HR 0.21, 95% CI 0.08-0.58). The benefit of any Hp test and treat prior to or at GC diagnosis was significant even among stage IV patients only (HR, 0.22; 95% CI 0.05-0.96). CONCLUSIONS: These findings support Hp testing and treatment for patients at risk of or diagnosed with GC, and suggest Hp treatment may provide an opportunity to reduce GC mortality disparities in the US.

Ductular and proliferative response of esophageal submucosal glands in a porcine model of esophageal injury and repair.

Esophageal injury is a risk factor for diseases such as Barrett's esophagus (BE) and esophageal adenocarcinoma. To improve understanding of signaling pathways associated with both normal and abnormal repair, animal models are needed. Traditional rodent models of esophageal repair are limited by the absence of esophageal submucosal glands (ESMGs), which are present in the human esophagus. Previously, we identified acinar ductal metaplasia in human ESMGs in association with both esophageal injury and cancer. In addition, the SOX9 transcription factor has been associated with generation of columnar epithelium and the pathogenesis of BE and is present in ESMGs. To test our hypothesis that ESMGs activate after esophageal injury with an increase in proliferation, generation of a ductal phenotype, and expression of SOX9, we developed a porcine model of esophageal injury and repair using radiofrequency ablation (RFA). The porcine esophagus contains ESMGs, and RFA produces a consistent and reproducible mucosal injury in the esophagus. Here we present a temporal assessment of this model of esophageal repair. Porcine esophagus was evaluated at 0, 6, 18, 24, 48, and 72 h and 5 and 7 days following RFA and compared with control uninjured esophagus. Following RFA, ESMGs demonstrated an increase in ductal phenotype, echoing our prior studies in humans. Proliferation increased in both squamous epithelium and ESMGs postinjury with a prominent population of SOX9-positive cells in ESMGs postinjury. This model promises to be useful in future experiments evaluating mechanisms of esophageal repair.NEW & NOTEWORTHY A novel porcine model of injury and repair using radiofrequency ablation has been developed, allowing for reproducible injury to the esophagus to study repair in an animal model with esophageal submucosal glands, a key anatomical feature and missing in rodent models but possibly harboring progenitor cells. There is a strong translational component to this porcine model given the anatomical and physiological similarities between pigs and humans.

TGF-ß-induced stromal CYR61 promotes resistance to gemcitabine in pancreatic ductal adenocarcinoma through downregulation of the nucleoside transporters hENT1 and hCNT3.

Pancreatic ductal adenocarcinoma (PDAC) is a lethal cancer in part due to inherent resistance to chemotherapy, including the first-line drug gemcitabine. Although low expression of the nucleoside transporters hENT1 and hCNT3 that mediate cellular uptake of gemcitabine has been linked to gemcitabine resistance, the mechanisms regulating their expression in the PDAC tumor microenvironment are largely unknown. Here, we report that the matricellular protein cysteine-rich angiogenic inducer 61 (CYR61) negatively regulates the nucleoside transporters hENT1 and hCNT3. CRISPR/Cas9-mediated knockout of CYR61 increased expression of hENT1 and hCNT3, increased cellular uptake of gemcitabine and sensitized PDAC cells to gemcitabine-induced apoptosis. In PDAC patient samples, expression of hENT1 and hCNT3 negatively correlates with expression of CYR61 . We demonstrate that stromal pancreatic stellate cells (PSCs) are a source of CYR61 within the PDAC tumor microenvironment. Transforming growth factor-ß (TGF-ß) induces the expression of CYR61 in PSCs through canonical TGF-ß-ALK5-Smad2/3 signaling. Activation of TGF-ß signaling or expression of CYR61 in PSCs promotes resistance to gemcitabine in PDAC cells in an in vitro co-culture assay. Our results identify CYR61 as a TGF-ß-induced stromal-derived factor that regulates gemcitabine sensitivity in PDAC and suggest that targeting CYR61 may improve chemotherapy response in PDAC patients.

Ductal metaplasia in oesophageal submucosal glands is associated with inflammation and oesophageal adenocarcinoma.

AIMS: Recent studies have suggested that oesophageal submucosal gland (ESMG) ducts harbour progenitor cells that may contribute to oesophageal metaplasia. Our objective was to determine whether histological differences exist between the ESMGs of individuals with and without oesophageal adenocarcinoma (EAC). METHODS AND RESULTS: We performed histological assessment of 343 unique ESMGs from 30 control patients, 24 patients with treatment-naïve high-grade columnar dysplasia (HGD) or EAC, and 23 non-EAC oesophagectomy cases. A gastrointestinal pathologist assessed haematoxylin and eosin-stained ESMG images by using a scoring system that assigns individual ESMG acini to five histological types (mucous, serous, oncocytic, dilated, or ductal metaplastic). In our model, ductal metaplastic acini were more common in patients with HGD/EAC (12.7%) than in controls (3.5%) (P = 0.006). We also identified greater proportions of acini with dilation (21.9%, P < 0.001) and, to a lesser extent, ductal metaplasia (4.3%, P = 0.001) in non-EAC oesophagectomy cases than in controls. Ductal metaplasia tended to occur in areas of mucosal ulceration or tumour. CONCLUSIONS: We found a clear association between ductal metaplastic ESMG acini and HGD/EAC. Non-EAC cases had dilated acini and some ductal dilation. Because ESMGs and ducts harbour putative progenitor cells, these associations could have significance for understanding the pathogenesis of EAC.

Endogenous elevation of plasma cholecystokinin does not prevent gallstones.

BACKGROUND: Regular gall bladder contraction reduces bile stasis and prevents gallstone formation. Intraduodenal administration of exogenous pancreatic secretory trypsin inhibitor-I (PSTI-I, also known as monitor peptide) causes cholecystokinin (CCK) secretion. DESIGN: We proposed that stimulation of CCK release by PSTI would produce gall bladder contraction and prevent gallstones in mice fed a lithogenic diet. Therefore, we tested the effect of overexpression of rat PSTI-I in pancreatic acinar cells on plasma CCK levels and gall bladder function in a transgenic mouse line (TgN[Psti1]; known hereafter as PSTI-I tg). RESULTS: Importantly, PSTI tg mice had elevated fasting and fed plasma CCK levels compared to wild-type (WT) mice. Only mice fed the lithogenic diet developed gallstones. Both fasting and stimulated plasma CCK levels were substantially reduced in both WT and PSTI-I tg mice on the lithogenic diet. Moreover, despite higher CCK levels PSTI-I tg animals developed more gallstones than WT animals. CONCLUSIONS: Together with the previously observed decrease in CCK-stimulated gall bladder emptying in mice fed a lithogenic diet, our findings suggest that a lithogenic diet causes gallstone formation by impaired CCK secretion in addition to reduced gall bladder sensitivity to CCK.

Two Accreditation Options for Biorepositories.

CONTEXT.­: Biomedical research relies on available biomaterials and associated data, and the quality of this starting material can have a significant impact on the quality of the experimental results. In the 2000s, best-practice documents and guidelines for biorepositories were published, followed in the 2010s by standards documents used to support accreditation. The College of American Pathologists Biorepository Accreditation Program and the International Standards Organization's standard 20387 were launched in 2012 and 2018, respectively. OBJECTIVE.­: To identify quantitative and qualitative differences between the two aforementioned biorepository accreditation standards for use by the larger biomedical research community; the results will empower biorepositories to select an accreditation program that best fits their goals. DESIGN.­: Individual requirements of both accreditation standards were identified and a bidirectional crosswalk was performed to identify gaps. Requirements were assigned to one of several standardized categories to enable comparison of the relative emphasis of different categories between the standards. RESULTS.­: Quantitatively, the College of American Pathologists program is comprehensive and stands alone, with 523 requirements, whereas the International Standards Organization program contains 167 requirements and is comprehensive through its incorporation and reference to numerous related standards documents. Qualitatively, both programs rely heavily on the implementation of an overarching quality management system and both programs can accommodate different types of biobanks (eg, human and animal). CONCLUSIONS.­: The standards differ in number of requirements, distribution of requirements across categories, and amount of reliance on separate standard documents. This information may aid in selection of an appropriate accreditation standard.

Prevalence of the cagA Virulence Factor Varies by Race Among Helicobacter pylori -Infected Patients Undergoing Upper Endoscopy.

INTRODUCTION: We designed a race-conscious study to assess the presence of Helicobacter pylori v irulence factor cagA in a retrospective cohort of patients with active H. pylori infection. METHODS: We compared cagA status by race in gastric tissue samples from 473 patients diagnosed with active H. pylori infection from 2015 to 2019. RESULTS: H. pylori + Black patients were 2 times more likely to be cagA + than H. pylori + White patients (82% vs 36%, P < .0001). DISCUSSION: Presence of cagA is common among endoscopy patients with active H. pylori infection; appropriate testing and treatment of H. pylori can both reduce gastric cancer risk and address health disparities.

Treatment Patterns and Clinical Outcomes Among Patients With Metastatic Prostate Cancer Harboring Homologous Recombination Repair Mutations.

BACKGROUND: There is currently limited literature assessing the real-world treatment patterns and clinical outcomes of patients with metastatic castration-resistant prostate cancer (mCRPC) and homologous recombination repair (HRR) mutations. METHODS: Medical charts were abstracted for mCRPC patients with ≥ 1 of 12 HRR somatic gene alterations treated at US oncology centers participating in the American Association for Cancer Research Project Genomics Evidence Neoplasia Information Exchange. Treatment patterns and clinical outcomes were assessed from the initiation of first-line or later (1L+) mCRPC therapy received on or after July 1, 2014. RESULTS: Among 138 patients included in the study, the most common somatic HRR mutations were CDK12 (47.8%), BRCA2 (22.5%), and ATM (21.0%). Novel hormonal therapy and taxane chemotherapy were most commonly used in 1L; taxane use increased in later lines. Median overall survival (95% confidence interval [CI]) was 36.3 (30.7-47.8) months from initiation of 1L therapy and decreased for subsequent lines. Similarly, there was a trend of decreasing progression-free survival and prostate-specific antigen response from 1L to 4L+ therapy. CONCLUSIONS: Treatment patterns identified in this study were similar to those among patients with mCRPC regardless of tumor HRR mutation status in the literature.

Mediator kinase inhibition impedes transcriptional plasticity and prevents resistance to ERK/MAPK-targeted therapy in KRAS-mutant cancers.

Acquired resistance remains a major challenge for therapies targeting oncogene activated pathways. KRAS is the most frequently mutated oncogene in human cancers, yet strategies targeting its downstream signaling kinases have failed to produce durable treatment responses. Here, we developed multiple models of acquired resistance to dual-mechanism ERK/MAPK inhibitors across KRAS-mutant pancreatic, colorectal, and lung cancers, and then probed the long-term events enabling survival against this class of drugs. These studies revealed that resistance emerges secondary to large-scale transcriptional adaptations that are diverse and cell line-specific. Transcriptional reprogramming extends beyond the well-established early response, and instead represents a dynamic, evolved process that is refined to attain a stably resistant phenotype. Mechanistic and translational studies reveal that resistance to dual-mechanism ERK/MAPK inhibition is broadly susceptible to manipulation of the epigenetic machinery, and that Mediator kinase, in particular, can be co-targeted at a bottleneck point to prevent diverse, cell line-specific resistance programs.

The Cooperative Human Tissue Network of the National Cancer Institute: Supporting Cancer Research for 35 Years.

The Cooperative Human Tissue Network was created by the NCI in 1987 to support a coordinated national effort to collect and distribute high quality, pathologist-validated human tissues for cancer research. Since then, the network has expanded to provide different types of tissue samples, blood and body fluid samples, immunohistologic and molecular sample preparations, tissue microarrays, and clinical datasets inclusive of biomarkers and molecular testing. From inception through the end of 2021, the network has distributed 1,375,041 biospecimens. It served 889 active investigators in 2021. The network has also taken steps to begin to optimize the representation of diverse communities among the distributed biospecimens. In this article, the authors review the 35-year history of this network, describe changes to the program over the last 15 years, and provide operational and scientific highlights from each of the divisions. Readers will learn how to engage with the network and about the continued evolution of the program for the future.

Pre-existing Castration-resistant Prostate Cancer-like Cells in Primary Prostate Cancer Promote Resistance to Hormonal Therapy.

BACKGROUND: Hormonal therapy targeting the androgen receptor inhibits prostate cancer (PCa), but the tumor eventually recurs as castration-resistant prostate cancer (CRPC). OBJECTIVE: To understand the mechanisms by which subclones within early PCa develop into CRPC. DESIGN, SETTING, AND PARTICIPANTS: We isolated epithelial cells from fresh human PCa cases, including primary adenocarcinoma, locally recurrent CRPC, and metastatic CRPC, and utilized single-cell RNA sequencing to identify subpopulations destined to become either CRPC-adeno or small cell neuroendocrine carcinoma (SCNC). OUTCOME MEASUREMENTS AND STATISTICAL ANALYSIS: We revealed dynamic transcriptional reprogramming that promotes disease progression among 23226 epithelial cells using single-cell RNA sequencing, and validated subset-specific progression using immunohistochemistry and large cohorts of publically available genomic data. RESULTS AND LIMITATIONS: We identified a small fraction of highly plastic CRPC-like cells in hormone-naïve early PCa and demonstrated its correlation with biochemical recurrence and distant metastasis, independent of clinical characteristics. We show that progression toward castration resistance was initiated from subtype-specific lineage plasticity and clonal expansion of pre-existing neuroendocrine and CRPC-like cells in early PCa. CONCLUSIONS: CRPC-like cells are present early in the development of PCa and are not exclusively the result of acquired evolutionary selection during androgen deprivation therapy. The lethal CRPC and SCNC phenotypes should be targeted earlier in the disease course of patients with PCa. PATIENT SUMMARY: Here, we report the presence of pre-existing castration-resistant prostate cancer (CRPC)-like cells in primary prostate cancer, which represents a novel castration-resistant mechanism different from the adaptation mechanism after androgen deprivation therapy (ADT). Patients whose tumors harbor increased pre-existing neuroendocrine and CRPC-like cells may become rapidly resistant to ADT and may require aggressive early intervention.

Leveraging patient derived models of FGFR2 fusion positive intrahepatic cholangiocarcinoma to identify synergistic therapies.

Intrahepatic cholangiocarcinoma (ICC) remains a deadly malignancy lacking systemic therapies for advanced disease. Recent advancements include selective FGFR1-3 inhibitors for the 15% of ICC patients harboring fusions, although survival is limited by poor response and resistance. Herein we report generation of a patient-derived FGFR2 fusion-positive ICC model system consisting of a cell line, organoid, and xenograft, which have undergone complete histologic, genomic, and phenotypic characterization, including testing standard-of-care systemic therapies. Using these FGFR2 fusion-positive ICC models, we conducted an unbiased high-throughput small molecule screen to prioritize combination strategies with FGFR inhibition, from which HDAC inhibition together with pemigatinib was validated in vitro and in vivo as a synergistic therapy for ICC. Additionally, we demonstrate broad utility of the FGFR/HDAC combination for other FGFR fusion-positive solid tumors. These data are directly translatable and justify early phase trials to establish dosing, safety, and therapeutic efficacy of this synergistic combination.

Characterization of a castrate-resistant prostate cancer xenograft derived from a patient of West African ancestry.

BACKGROUND: Prostate cancer is a clinically and molecularly heterogeneous disease, with highest incidence and mortality among men of African ancestry. To date, prostate cancer patient-derived xenograft (PCPDX) models to study this disease have been difficult to establish because of limited specimen availability and poor uptake rates in immunodeficient mice. Ancestrally diverse PCPDXs are even more rare, and only six PCPDXs from self-identified African American patients from one institution were recently made available. METHODS: In the present study, we established a PCPDX from prostate cancer tissue from a patient of estimated 90% West African ancestry with metastatic castration resistant disease, and characterized this model's pathology, karyotype, hotspot mutations, copy number, gene fusions, gene expression, growth rate in normal and castrated mice, therapeutic response, and experimental metastasis. RESULTS: This PCPDX has a mutation in TP53 and loss of PTEN and RB1. We have documented a 100% take rate in mice after thawing the PCPDX tumor from frozen stock. The PCPDX is castrate- and docetaxel-resistant and cisplatin-sensitive, and has gene expression patterns associated with such drug responses. After tail vein injection, the PCPDX tumor cells can colonize the lungs of mice. CONCLUSION: This PCPDX, along with others that are established and characterized, will be useful pre-clinically for studying the heterogeneity of prostate cancer biology and testing new therapeutics in models expected to be reflective of the clinical setting.

Automated next-generation profiling of genomic alterations in human cancers.

The lack of validated, distributed comprehensive genomic profiling assays for patients with cancer inhibits access to precision oncology treatment. To address this, we describe elio tissue complete, which has been FDA-cleared for examination of 505 cancer-related genes. Independent analyses of clinically and biologically relevant sequence changes across 170 clinical tumor samples using MSK-IMPACT, FoundationOne, and PCR-based methods reveals a positive percent agreement of >97%. We observe high concordance with whole-exome sequencing for evaluation of tumor mutational burden for 307 solid tumors (Pearson r = 0.95) and comparison of the elio tissue complete microsatellite instability detection approach with an independent PCR assay for 223 samples displays a positive percent agreement of 99%. Finally, evaluation of amplifications and translocations against DNA- and RNA-based approaches exhibits >98% negative percent agreement and positive percent agreement of 86% and 82%, respectively. These methods provide an approach for pan-solid tumor comprehensive genomic profiling with high analytical performance.

X-ray fan beam coded aperture transmission and diffraction imaging for fast material analysis.

X-ray transmission imaging has been used in a variety of applications for high-resolution measurements based on shape and density. Similarly, X-ray diffraction (XRD) imaging has been used widely for molecular structure-based identification of materials. Combining these X-ray methods has the potential to provide high-resolution material identification, exceeding the capabilities of either modality alone. However, XRD imaging methods have been limited in application by their long measurement times and poor spatial resolution, which has generally precluded combined, rapid measurements of X-ray transmission and diffraction. In this work, we present a novel X-ray fan beam coded aperture transmission and diffraction imaging system, developed using commercially available components, for rapid and accurate non-destructive imaging of industrial and biomedical specimens. The imaging system uses a 160 kV Bremsstrahlung X-ray source while achieving a spatial resolution of ≈ 1 × 1 mm2 and a spectral accuracy of > 95% with only 15 s exposures per 150 mm fan beam slice. Applications of this technology are reported in geological imaging, pharmaceutical inspection, and medical diagnosis. The performance of the imaging system indicates improved material differentiation relative to transmission imaging alone at scan times suitable for a variety of industrial and biomedical applications.

Next-Generation Sequencing Concordance Analysis of Comprehensive Solid Tumor Profiling between a Centralized Specialty Laboratory and the Decentralized Personal Genome Diagnostics elio Tissue Complete Kitted Solution.

Genomic tumor profiling by next-generation sequencing (NGS) allows for large-scale tumor testing to inform targeted cancer therapies and immunotherapies, and to identify patients for clinical trials. These tests are often underutilized in patients with late-stage solid tumors and are typically performed in centralized specialty laboratories, thereby limiting access to these complex tests. Personal Genome Diagnostics Inc., elio tissue complete NGS solution is a comprehensive DNA-to-report kitted assay and bioinformatics solution. Comparison of 147 unique specimens from >20 tumor types was performed using the elio tissue complete solution and Foundation Medicine's FoundationOne test, which is of similar size and gene content. The analytical performance of all genomic variant types was evaluated. In general, the overall mutational profile is highly concordant between the two assays, with agreement in sequence variants reported between panels demonstrating >95% positive percentage agreement for single-nucleotide variants and insertions/deletions in clinically actionable genes. Both copy number alterations and gene translocations showed 80% to 83% positive percentage agreement, whereas tumor mutation burden and microsatellite status showed a high level of concordance across a range of mutation loads and tumor types. The Personal Genome Diagnostics Inc., elio tissue complete assay is comparable to the FoundationOne test and will allow more laboratories to offer a diagnostic NGS assay in house, which will ultimately reduce time to result and increase the number of patients receiving molecular genomic profiling and personalized treatment.

Implementation of a Molecular Tumor Registry to Support the Adoption of Precision Oncology Within an Academic Medical Center: The Duke University Experience.

Comprehensive genomic profiling to inform targeted therapy selection is a central part of oncology care. However, the volume and complexity of alterations uncovered through genomic profiling make it difficult for oncologists to choose the most appropriate therapy for their patients. Here, we present a solution to this problem, The Molecular Registry of Tumors (MRT) and our Molecular Tumor Board (MTB). PATIENTS AND METHODS: MRT is an internally developed system that aggregates and normalizes genomic profiling results from multiple sources. MRT serves as the foundation for our MTB, a team that reviews genomic results for all Duke University Health System cancer patients, provides notifications for targeted therapies, matches patients to biomarker-driven trials, and monitors the molecular landscape of tumors at our institution. RESULTS: Among 215 patients reviewed by our MTB over a 6-month period, we identified 176 alterations associated with therapeutic sensitivity, 15 resistance alterations, and 51 alterations with potential germline implications. Of reviewed patients, 17% were subsequently treated with a targeted therapy. For 12 molecular therapies approved during the course of this work, we identified between two and 71 patients who could qualify for treatment based on retrospective MRT data. An analysis of 14 biomarker-driven clinical trials found that MRT successfully identified 42% of patients who ultimately enrolled. Finally, an analysis of 4,130 comprehensive genomic profiles from 3,771 patients revealed that the frequency of clinically significant therapeutic alterations varied from approximately 20% to 70% depending on the tumor type and sequencing test used. CONCLUSION: With robust informatics tools, such as MRT, and the right MTB structure, a precision cancer medicine program can be developed, which provides great benefit to providers and patients with cancer.

Results and Clinical Utilization of Foundation Medicine Molecular Tumor Profiling in Uterine and Ovarian Cancers.

BACKGROUND: Recent advances in next-generation sequencing have allowed for an increase in molecular tumor profiling. OBJECTIVE: We sought to assess the actionability and clinical utilization of molecular tumor profiling results obtained via Foundation Medicine tumor sequencing tests in uterine and ovarian cancers. PATIENTS AND METHODS: We performed a single-institution retrospective chart review to obtain demographic and clinical information in patients with uterine and ovarian cancer whose tumors were submitted to Foundation Medicine for molecular tumor profiling over a 7-year period. Alterations identified on testing were stratified according to the OncoKB database actionability algorithm. Descriptive statistics were primarily used to analyze the data. RESULTS: Tumors from 185 women with gynecologic cancer were submitted for molecular tumor profiling between 2013 and 2019. The majority of tests (144/185; 78%) were ordered after a diagnosis of recurrence. In 60 (32%), no actionable molecular alteration was identified. Thirteen (7%) identified an alteration that directed to a US Food and Drug Administration-approved therapy in that tumor type, while 112 (61%) had alterations with investigational or hypothetical treatment implications. In patients with any actionable finding, treatment was initiated in 27 (15%) based on these results. CONCLUSIONS: The majority of uterine and ovarian cancers (93%) did not have molecular alterations with corresponding Food and Drug Administration-approved treatments. Even in patients with a potentially actionable alteration, gynecologic oncologists were more likely to choose an alternative therapy. Further investigation is warranted to determine which patients with uterine and ovarian cancer are most likely to benefit from molecular tumor profiling and the ideal timing of testing. The potential to identify effective therapeutic options in a minority of patients needs to be balanced with the current limited clinical applicability of these results in most cases.

Reduced MFAP5 expression in stroma of gallbladder adenocarcinoma and its potential diagnostic utility.

The diagnosis of invasive adenocarcinoma of the gallbladder can sometimes be challenging. The presence of true desmoplastic reaction facilitates the diagnosis of invasion. However, desmoplasia-like changes can be observed in benign gallbladder conditions, and recognition of desmoplasia may be challenging based on morphology. In this study, we tested the expression pattern of microfibril-associated protein 5 (MFAP5), a promising immunohistochemical marker for desmoplasia, in benign gallbladders with desmoplasia-like reaction and gallbladders with invasive adenocarcinoma. We also evaluated the diagnostic utility of MFAP5 in challenging cases with an interobserver agreement study. The results showed that all benign cases retained intact/positive MFAP5 staining pattern in periglandular connective tissue, whereas 79.3% (23 out of 29) of cases of adenocarcinomas demonstrated diffuse and complete loss of MFAP5 staining in the tumor stroma. Interobserver agreement was improved by 2.66 times when images of MFAP5 immunohistochemistry were provided. In conclusion, MFAP5 expression is downregulated in the desmoplastic stroma of gallbladder adenocarcinoma and may provide a useful diagnostic marker in difficult cases.