Journal Of Pathology Research Articles

Activated immune infiltrates expand opportunities for targeted therapy in p53-abnormal endometrial carcinoma.

Tumor protein p53 mutated/abnormal (p53abn) endometrial carcinomas account for over 50% of deaths but comprise only 15% of all endometrial carcinomas. Most patients show limited response to standard-of-care chemotherapy with or without radiotherapy, and only a minority of cases are amenable to targeted therapies like poly-ADP ribose polymerase (PARP) inhibitors and HER2-directed therapies. Recent immunotherapy clinical trials have demonstrated remarkable efficacy, not only in mismatch repair deficient (MMRd) tumors but also in a subset of mismatch repair-proficient (MMRp) tumors. However, the immune microenvironment and its relationship to other therapeutic targets in MMRp endometrial carcinoma remains poorly understood. Here, we characterize the immune microenvironment of p53abn endometrial carcinoma, the most clinically aggressive subtype of MMRp endometrial carcinoma, and correlate antitumor immune signatures with other targetable alterations. We accrued 256 treatment-naïve p53abn endometrial carcinomas and systemically profiled T-cell, B-cell, myeloid, and tumor-cell populations with multiplex immunofluorescence to assess the tissue localization and functional status of immune cells. Shallow whole-genome sequencing was performed on a subset of 126 cases. Patterns of immune infiltration were compared to survival outcomes and mutational signatures. Mixture modeling divided p53abn endometrial carcinoma into tumor-infiltrating lymphocyte (TIL)-rich and TIL-poor subsets. Over 50% of tumors were TIL-rich. TIL-rich cases overexpressed targetable immune evasion molecules and were associated with longer overall and disease-specific survival in multivariate analysis. This effect was particularly pronounced in advanced stage disease and in patients who did not receive adjuvant chemotherapy. TIL did not associate with homologous recombination deficient mutational signatures or HER2 amplification. Our findings demonstrate a biological rationale for immunotherapy in a substantial subset of patients with p53abn endometrial cancer and may help inform combination therapies with immune checkpoint inhibition, PARP inhibitors, and anti-HER2 agents. © 2025 The Author(s). The Journal of Pathology published by John Wiley & Sons Ltd on behalf of The Pathological Society of Great Britain and Ireland.

Aberrant TERT expression: linking chronic inflammation to hepatocellular carcinoma†.

Telomerase reverse transcriptase (TERT), the catalytic enzyme component of telomerase, plays multiple roles in cellular biology. Its canonical function is primarily associated with telomere maintenance and genomic stability. In addition, several studies revealed critical non-canonical extra-telomeric functions of TERT in various cellular processes, including cell proliferation and survival, DNA damage response, transcription, signal transduction, and metabolic regulation, both in normal and in cancer cells. Notably, TERT is aberrantly upregulated in more than 80% of hepatocellular carcinoma (HCC) cases, making it an important target in liver cancer research. However, due to the diversity and complexity of TERT's functions in vivo, the precise mechanisms by which TERT contributes to the initiation and progression of HCC remain unclear. A recent study published in The Journal of Pathology using the Alb-Cre;TertTg mouse model and clinical HCC samples addresses the role of TERT in hepatocarcinogenesis. The study demonstrates that TERT promotes cell cycle progression and hepatocarcinogenesis by enhancing NF-κB promoter activity and facilitating the ubiquitination of p21. Notably, absence of functional p53 accelerates liver tumor development in TERT transgenic mice. These findings further underscore the critical role of TERT in inflammation-driven hepatocarcinogenesis and provide new insights into its underlying mechanisms. © 2025 The Author(s). The Journal of Pathology published by John Wiley & Sons Ltd on behalf of The Pathological Society of Great Britain and Ireland.

BMP signalling in colorectal cancer: losing the yin to WNTs yang.

Colorectal cancer (CRC) is the third most common form of cancer globally, and arises from the hyperproliferation of epithelial cells in the intestine. The architecture and maintenance of these cells is governed by two major signalling pathways working in a counter-gradient: the stem cell WNT signalling pathway, and the prodifferentiation bone morphogenetic protein (BMP) pathway. It has long been known that this WNT-BMP balance is disrupted in CRC, with hyperactive WNT signalling leading to increased proliferation of epithelial cells and tumour progression. BMP signalling, and its prodifferentiation effects, have increasingly become a focus for CRC research. Loss of BMP signalling, and that of its receptors, has been shown to increase WNT signalling and cancer stem cells in CRC. BMP signalling is further modulated through secreted BMP antagonists localised to the intestinal crypts, which create a niche ensuring that sustained WNT signalling can maintain stem-cell self-renewal capacity. A number of studies combine to demonstrate the effects of overexpression of these BMP antagonists, showing that hyperactivity of the stem-cell-supporting WNT signalling pathway ensues, leading to deregulation of the intestinal epithelium. Cellular hyperproliferation, the emergence of ectopic crypts, and an increase in stem cell numbers and characteristics are common themes, contributing to disrupted epithelial homeostasis, an increase in CRC risk and progression, and resistance to therapy. This review aims to compile the current knowledge on BMP antagonists, their role in CRC development, and how we can utilise this information for biomarker research and novel therapeutics. © 2025 The Author(s). The Journal of Pathology published by John Wiley & Sons Ltd on behalf of The Pathological Society of Great Britain and Ireland.

Global Insights of Oral Submucous Fibrosis: Concerns About Betel Nut and Oral Cancer.

Oral submucous fibrosis (OSF) is a chronic progressive fibrosis of oral mucosa, with the possibility of eventually progressing to oral cancer, remaining unclear pathogenesis, and a lack of targeted therapies. This study aims to analyze current research progress from a bibliometric perspective to guide the way forward. Documents in the Web of Science Core Collection database from 1999 to August 31, 2023 were thoroughly searched using a given query. After selection, years of publishing, countries, institutions, authors, journals, and keywords were analyzed using bibliometric software. The bibliometric results of 1522 documents show that India and China were the most productive countries in this field. Central South University has published the most papers. The Journal of Oral Pathology & Medicine and Oral Oncology were the leading journals. Betel nut, oral cancer, malignant transformation, and fibroblast were the main focuses during recent study periods. We also analyzed differences between studies in betel chewing and nonchewing areas. Notably, scholars pay more attention to the pathogenesis of OSF in the former, while the relationship between OSF and cancer is more concerning in the latter, such as in the United Kingdom and the United States. Findings from this study provide an overview of the current research and reveal the future hotspot of the OSF research. It suggests that exploring the pathogenesis and mechanisms of malignant transformation in OSF will be a focal point in future research. Advancements in the prevention and treatment of OSF could significantly enhance patients' quality of life and reduce mortality associated with oral cancer.

Advances in haematolymphoid pathology in China over the past ten years: retrospect and prospect

In the past decade, significant progress has been made in the field of haematolymphoid pathology in China. Domestic experts have published nearly 100 articles in the Chinese Journal of Pathology and international authoritative journals. These achievements have deepened the fundamental theoretical research of haematolymphoid pathology and significantly improved the clinical pathological diagnosis level, providing valuable Chinese data for the pathological diagnosis and research of haematolymphoid diseases internationally. In addition, the domestic haematolymphoid pathological diagnosis and training system has been comprehensively optimized, with closer interaction and integration with clinical medicine, cultivating a large number of specialized pathologists, and driving innovation and development of the entire pathology discipline.

Shifts in Cutaneous Melanocytic Tumor Diagnostic Terminology: Melanocytoma, MPATH‐Dx V2.0 and the WHO Skin5

ABSTRACTIn this Special Issue of the Journal of Cutaneous Pathology in memory of Dr. Martin C. Mihm, Jr, we highlight his many contributions over more than 50 years to the catalog of specific melanocytic tumor terminology. Dr. Mihm was an active participant in the International Melanoma Pathology Study Group (IMPSG). Discussions led to proposed recommendations for changes in the terminology of melanocytic tumors and their standardized diagnostic reporting. Histopathological reports of melanocytic tumors provide critical information that guides patient counseling and therapy. Importantly the pathology report must relay whether the melanocytic tumor is benign, intermediate, or malignant, and when appropriate, indicate diagnostic and/or prognostic uncertainty. Recent shifts in diagnostic terminology include the recommended use of the term “melanocytoma” to describe a morphologically and genetically defined subset of intermediate risk melanocytic tumors with higher (although still very low) risk of progression compared with benign nevi. Melanocytomas are distinguished from melanocytic tumors of uncertain malignant potential (MELTUMP) which are histopathologically indeterminate or uncertain tumors. In the setting of a broad lexicon for the reporting of melanocytic tumors, an assessment tool has been developed to map existing diverse terminologies into distinct hierarchical classes. The Melanocytic Pathology Assessment Tool and Hierarchy for Diagnosis (MPATH‐Dx) V2.0 provides a four‐tiered classification scheme that is tiered by risk of tumor progression and recommended treatment. The purpose of this review is to report these shifts in diagnostic terminology, discussed and reviewed at the annual workshop of the IMPSG, in Edinburg, Scotland, in November 2022. This discussion included the use of the term melanocytoma, and the use of the MPATH‐Dx V2.0 classification and terminology for melanocytic tumors. Dr. Mihm was diligent in his attention to specific terminology, in his memory we aim to recommend terminology that improves communication in the care of those diagnosed with melanocytic tumors.

Histologic and molecular features shared between antibody-mediated rejection of kidney allografts and chronic histiocytic intervillositis support common pathogenesis.

Chronic histiocytic intervillositis (CHI) is an inflammatory condition of the placenta, characterised by an abnormal, mainly macrophagic infiltrate within the intervillous space. Recent research suggests that CHI results from a 'maternal-foetal rejection' mechanism, because at least some CHI cases fulfil the criteria for antibody-mediated rejection (AMR) of kidney allografts according to the Banff classification [i.e. presence of anti-human leukocyte antigen (HLA) paternal antibodies activating the complement or foetal-specific antibodies (FSA), a macrophage-rich infiltrate, and positive C4d immunostaining]. To gain further insights into CHI pathogenesis, we aimed to refine the phenotype of the inflammatory infiltrate using a multiplex immunofluorescence technique and to compare the mRNA signatures between CHI and AMR of kidney allografts. Twelve patients with C4d + FSA+ CHI were included in the study and compared to a control group of 5 patients without inflammatory lesions on placental examination. We developed a multiplex immunofluorescence panel to identify CD4+ and CD8+ T lymphocytes, CD68+/CD206- and CD68+/CD206+ macrophages, and NK cells in the villi and intervillous space. Molecular signatures were studied using NanoString® technology and the B-HOT panel recommended by the Banff classification for kidney allografts. Multiplex immunofluorescence revealed that the infiltrate in the intervillous space was mainly composed of CD68+/CD206- macrophages as well as a higher proportion of CD8+ lymphocytes in patients with CHI compared to controls. Densities of NK cells and CD4 T cells were very low. Molecular signatures showed an overexpression of HLA class II genes, an IFN-γ signature, and cytokine gene sets in C4d + FSA+ CHI patients, also involved in kidney AMR. These results reinforce the paradigm of maternal-foetal rejection. © 2025 The Author(s). The Journal of Pathology published by John Wiley & Sons Ltd on behalf of The Pathological Society of Great Britain and Ireland.

A Tc1‐ and Th1‐T‐lymphocyte‐rich tumor microenvironment is a hallmark of MSI colorectal cancer

AbstractMicrosatellite instability is a strong predictor of response to immune checkpoint therapy and patient outcome in colorectal cancer. Although enrichment of distinct T‐cell subpopulations has been determined to impact the response to immune checkpoint therapy and patient outcome, little is known about the underlying changes in the composition of the immune tumor microenvironment. To assess the density, composition, degree of functional marker expression, and spatial interplay of T‐cell subpopulations, 79 microsatellite instable (MSI) and 1,045 microsatellite stable (MSS) colorectal cancers were analyzed. A tissue microarray and large sections were stained with 19 antibodies directed against T cells, antigen‐presenting cells, functional markers, and structural proteins using our BLEACH&STAIN multiplex‐fluorescence immunohistochemistry approach. A deep learning‐based framework comprising >20 different convolutional neuronal networks was developed for image analysis. The composition of Type 1 (T‐bet+), Type 2 (GATA3+), Type 17 (RORγT+), NKT‐like (CD56+), regulatory (FOXP3+), follicular (BCL6+), and cytotoxic (CD3+CD8+) or helper (CD3+CD4+) T cells showed marked differences between MSI and MSS patients. For instance, the fraction of Tc1 and Th1 was significantly higher (p < 0.001 each), while the fraction of Tregs, Th2, and Th17 T cells was significantly lower (p < 0.05) in MSI compared to MSS patients. The degree of TIM3, CTLA‐4, and PD‐1 expression on most T‐cell subpopulations was significantly higher in MSI compared to MSS patients (p < 0.05 each). Spatial analysis revealed increased interactions between Th1, Tc1, and dendritic cells in MSI patients, while in MSS patients the strongest interactions were found between Tregs, Th17, Th2, and dendritic cells. The additional analysis of 12 large sections revealed a divergent immune composition at the invasive margin. In summary, this study identified a higher fraction of Tc1 and Th1 T cells accompanied by a paucity of regulatory T‐cell, Th17, and Th2 T‐cell subpopulations, along with a distinct interaction profile, as a hallmark of MSI compared to MSS colorectal cancers. © 2025 The Author(s). The Journal of Pathology published by John Wiley & Sons Ltd on behalf of The Pathological Society of Great Britain and Ireland.

MicroRNA-371-373 cluster and methylome analysis suggests that a subset of 'somatic-type' malignancies arising in germ cell tumors may originate in yolk sac tumor components.

Somatic-type malignancies (SMs) arising in germ cell tumors (GCTs) are aggressive neoplasms resistant to systemic treatment. Most are diagnosed in metastatic sites after chemotherapy; however, they have also been well-documented in primary testicular GCTs. Historically, SMs were thought to originate in components of teratoma that acquire molecular alterations equivalent to those that characterize their true somatic counterparts. However, recent studies have shown that SMs typically lack the hallmark molecular alterations seen in similar somatic tumors. Additionally, clinicopathologic and molecular data suggest that a subset may derive from yolk sac tumor (YST) rather than teratoma. In this study, we evaluated the relationship between conventional histological types of GCTs and SMs by comparingexpression of microRNA (miR)-371-373 and genomicmethylation profiles. A total of 96 samples (including multiple paired conventional GCT-SM samples from individual tumors)were assessed for miR-371-373 expression by RT-qPCR and genomic DNA methylation using a clinically validated assay. Expression of miR-371-373 was higher in conventional GCTs than in SMs (considered as a single category encompassing all histological subtypes). However, miR-371-373 expression was heterogeneous among SMs, with significantly higher levels in sarcomatoid YST (SYST) and glandular neoplasms than in other SMs. Genomic DNA methylation analysis showed that SMs (considered as a single category) did not form a distinct cluster. Instead, they grouped into multiple clusters that did not show perfect correspondence with histology and often included conventional GCTs. Genome-wide methylation assessment showed a higher abundance of hypermethylatedregions in SMs than in conventional GCTs. Analysis of paired conventional GCT and 'somatic-type' components that did not meet size criteria for SMs dissected from individual tumors demonstrated separation according to histology, suggesting that epigenetic processes play a role in the transition from conventional GCT to 'somatic-type' phenotypes. Gene-level and pathway-level analyses identified MAPK/RAS signaling, mitosis/proliferation, differentiation towards neural tissue/neuroectoderm, epithelial-to-mesenchymal transition, and DNA repair as key differentially regulated processes in components with somatic-type histology, suggesting mechanisms of progression from conventional to 'somatic' phenotypes in GCT. These results support the hypothesis that a subset of SMs derive from YST and suggest that some subtypes (such as SYST) may represent 'intermediate' phenotypes. Additionally, analysis of differentially methylated promoter regions in SM identified genes and biologic processess that may underlie 'somatic tranformation' in GCTs. © 2025 The Author(s). The Journal of Pathology published by John Wiley & Sons Ltd on behalf of The Pathological Society of Great Britain and Ireland.

A breast cancer PDX collection enriched in luminal (ER+) tumors and young premenopausal patients to identify new therapeutic strategies for high-risk patients†.

Breast cancer includes a group of neoplasms originating from mammary gland epithelial cells caused by a variety of genetic alterations, with different responses to treatments and outcomes. In clinical practice, estrogen receptor (ER), progesterone receptor (PR), and human epidermal growth factor receptor 2 (HER2) expression guides the distinction between luminal A (ER+, PR+, HER2-), luminal B (ER+, PR+, HER2+/-), and triple-negative (ER-, PR-, HER2-), each with a distinct biological behavior and clinical and therapeutic implications. Approximately 11% of breast cancers are diagnosed in young premenopausal women aged 20-49 years. Patient-derived xenografts (PDXs) offer a powerful solution to integrate personalized medicine and novel therapeutic agents. Dr Belletti's group recently developed a PDX biobank composed of 26 PDX lines highly enriched in luminal A and B and young premenopausal breast cancer patients. The bank faithfully recapitulates the characteristics of the original tumors. A major focus of their research was to exploit these PDXs to assess the resistance to CDK4/6 inhibitors (CDK4/6i), which are critical in managing advanced luminal breast cancers. Their effort addresses a significant gap in existing PDX models, which are limited for these patient subgroups, thereby enabling deeper insights into tumor biology and therapeutic responses in these understudied populations. © 2025 The Author(s). The Journal of Pathology published by John Wiley & Sons Ltd on behalf of The Pathological Society of Great Britain and Ireland.

Cancer-associated fibroblast heterogeneity in chordoma†.

In solid tumours, malignant cells develop relationships with nonmalignant stromal cells to support tumour growth, tissue structure, and nutrient supply. In a recent issue of this journal, Zheng and Guo catalogue the cellular landscape in chordoma using a combination of single-cell and spatial transcriptomics. Despite the mesenchymal nature of chordoma, malignant cells retain expression of epithelial markers, in addition to mesenchymal, partial-EMT, and stem-cell signatures. Cancer-associated fibroblasts (CAFs) are among the most abundant stromal cells and the authors define an inflammatory CAF subtype (iCAF), which is associated with poor outcome and tumour invasion. It is proposed that iCAFs arise from normal fibroblasts during malignant tumour progression and play a causative role in driving an invasive poor prognosis tumour phenotype. Recent reports by this and other groups have separately catalogued cell populations, including CAFs and immune cells in chordoma. The next challenge will be to integrate findings from these distinct studies to allow a consensus to be reached regarding cellular heterogeneity within chordoma, and to allow comparison of CAF populations with those found in other tumour types. Comparison of CAF functions in these predominantly mesenchymal tumours with epithelial solid tumours may reveal interesting lessons about the diverse phenotypes CAFs can bring to distinct tumour ecosystems. Understanding the role of CAFs in chordoma progression may also lead to therapeutic opportunities, but separation of correlation and causation in CAF regulation of tumour phenotypes remains a significant challenge. © 2025 The Author(s). The Journal of Pathology published by John Wiley & Sons Ltd on behalf of The Pathological Society of Great Britain and Ireland.

The significance of PAX5 in Merkel cell carcinoma.

Merkel cell carcinoma (MCC) is a highly malignant skin cancer that expresses epithelial-, neuroendocrine-, and lymphoid-associated genes. Here, we focused on B-cell differentiation, which is characterised by the coexpression of PAX5 and TdT. PAX5 is the master regulator of B-cell commitment and is expressed in 65% of MCC cases. Yet little is known about the underlying molecular biology of the frequently reported PAX5 expression in MCC. Multi-omics analyses, including RNA next-generation sequencing, RT-qPCR, immunohistochemistry, and western blotting, were performed to assess PAX5 expression in MCC. Differential DNA methylation analysis at 61,043 PAX5 binding sites in enhancer and promoter elements was performed to detect differences between n = 14 MCC tissues and n = 91 various normal B-cell populations. RNA analysis revealed full-length PAX5 expression in MCC at the transcriptional level using both PAX5 transcription start sites. PAX5 protein expression was found in 40 of 41 MCCs and six out of seven MCC cell lines. DNA methylation array analysis revealed 1,084 hypermethylated loci of enhancer and promoter elements located in PAX5 binding sites in MCC. Of these, 702 loci were associated with 257 genes that are not expressed. The PAX5-associated regulatory elements of these 257 genes were enriched for interferon regulatory factor 4 (IRF4) and SPi-proto-oncogene (SPI1) binding motifs. Neither IRF4 or SPI1 could be detected in MCC on RNA or the protein level. Thus, because of the absence of these transcription factors, we conclude that full-length PAX5 alone cannot induce B-cell differentiation. © 2025 The Author(s). The Journal of Pathology published by John Wiley & Sons Ltd on behalf of The Pathological Society of Great Britain and Ireland.

Afadin loss induces breast cancer metastasis through destabilisation of E-cadherin to F-actin linkage.

Afadin is a multimodal scaffolding protein with essential functions in cell-cell adhesion. Although its loss of expression has been linked to breast cancer invasion and metastasis, the underlying mechanisms driving tumour progression upon mutational Afadin (AFDN) loss in breast cancers remains unclear. In the current study we identified a somatic frameshift AFDN mutation (p.Lys630fs) in an invasive breast cancer sample that coincides with loss of Afadin protein expression. Functional studies in E-cadherin-expressing breast cancer cells show that Afadin loss leads to immature and aberrant adherens junction (AJ) formation. The lack of AJ maturation results in a noncohesive cellular phenotype accompanied by Actomyosin-dependent anoikis resistance, which are classical progression hallmarks of single-cell breast cancer invasion. Reconstitution experiments using Afadin truncates show that proper F-actin organisation and epithelial cell-cell adhesion critically depend on the Coiled-Coil domain of Afadin but not on the designated C-terminal F-actin binding domain. Mouse xenograft experiments based on cell lines and primary patient-derived breast cancer organoids demonstrate that Afadin loss induces single-cell lobular-type invasion phenotypes and overt dissemination to the lungs and the peritoneum. In short, Afadin is a metastasis suppressor for breast cancer through stabilisation and maturation of a mechanical E-cadherin to F-actin outside-in link. © 2025 The Author(s). The Journal of Pathology published by John Wiley & Sons Ltd on behalf of The Pathological Society of Great Britain and Ireland.

Multiomic spatial atlas shows deleted in malignant brain tumors 1 (DMBT1) glycoprotein is lost in colonic dysplasia.

Colorectal cancer (CRC) is responsible for over 900,000 annual deaths worldwide. Emerging evidence supports pro-carcinogenic bacteria in the colonic microbiome are at least promotional in CRC development and may be causal. We previously showed toxigenic C. difficile from human CRC-associated bacterial biofilms accelerates tumorigenesis in ApcMin/+ mice, both in specific pathogen-free mice and in gnotobiotic mice colonized with a defined consortium of bacteria. To further understand host-microbe interactions during colonic tumorigenesis, we combined single-cell RNA-sequencing (scRNA-seq), spatial transcriptomics, and immunofluorescence to define the molecular spatial organization of colonic dysplasia in our consortium model with or without C. difficile. Our data show a striking bipartite regulation of Deleted in Malignant Brain Tumors 1 (DMBT1) in the inflamed versus dysplastic colon. From scRNA-seq, differential gene expression analysis of normal absorptive colonocytes at 2 weeks postinoculation showed DMBT1 upregulated by C. difficile compared to colonocytes from mice without C. difficile exposure. In contrast, our spatial transcriptomic analysis showed DMBT1 dramatically downregulated in dysplastic foci compared with normal-adjacent tissue. We further integrated our datasets to generate custom colonic dysplasia scores and ligand-receptor mapping. Validation with immunofluorescence showed DMBT1 protein downregulated in dysplastic foci from three mouse models of colonic tumorigenesis and in adenomatous dysplasia from human samples. Finally, we used mouse and human organoids to implicate WNT signaling in the downregulation of DMBT1 mRNA and protein. Together, our data reveal cell type-specific regulation of DMBT1, a potential mechanistic link between bacteria and colonic tumorigenesis. Published 2025. This article is a U.S. Government work and is in the public domain in the USA. The Journal of Pathology published by John Wiley & Sons Ltd on behalf of The Pathological Society of Great Britain and Ireland.

Cellular origins of mucinous ovarian carcinoma.

Mucinous ovarian carcinoma (MOC) is a rare histotype of epithelial ovarian cancer. Its origins are obscure: while many mucinous tumours in the ovary are metastases from the gastrointestinal tract, MOC can occur as an ovarian primary; however, the cell of origin is not well established. In this review we summarise the pathological, epidemiological, and molecular evidence for the cellular origins of MOC. We propose a model for the origins of the various tumours of the ovary with mucinous differentiation. We distinguish Müllerian from gastrointestinal-type mucinous differentiation. A small proportion of the latter arise from teratoma and a distinct terminology has been proposed. Other gastrointestinal mucinous tumours are associated with Brenner tumours and arise from their associated benign lesions, Walthard nests. The remaining mucinous tumours develop either through mucinous metaplasia in established Müllerian tumours or with even greater plasticity through gastrointestinal metaplasia of epithelial or mesothelial ovarian inclusions. This model remains to be validated and mechanistically understood and we discuss future research directions. © 2025 The Author(s). The Journal of Pathology published by John Wiley & Sons Ltd on behalf of The Pathological Society of Great Britain and Ireland.

Platelet C3G protects from liver fibrosis, while enhancing tumor growth through regulation of the immune response.

Primary liver cancer usually occurs in the context of chronic liver disease (CLD), in association with fibrosis. Platelets have emerged as important regulators of CLD and liver cancer, although their precise function and mechanism of action need to be clarified. C3G (RapGEF1) regulates platelet activation, adhesion, and secretion. Here we evaluate the role of platelet C3G in chemically induced fibrosis and liver cancer associated with fibrosis using genetically modified mouse models. We found that while overexpression of full-length C3G in platelets decreased liver fibrosis induced by chronic treatment with CCl4, overexpressed C3G lacking the catalytic domain did not, although in both cases platelet recruitment to the liver was similar. In addition, C3G deletion in platelets (PF4-C3GKO mouse model) increased CCl4-induced liver damage and hepatic fibrosis, reducing liver platelets and macrophages. Moreover, early liver immune response to CCl4 was altered in PF4-C3GKO mice, with a remarkable lower activation of macrophages and increased monocyte-derived macrophages compared to WT mice. On the other hand, in response to DEN+CCl4, PF4-C3G WT mice exhibited more and larger liver tumors than PF4-C3GKO mice, accompanied by the presence of more platelets, despite having less fibrosis in previous steps. Liver immune cell populations were also differentially regulated in PF4-C3GKO mice, highlighting the higher number of macrophages, likely with a pro-inflammatory phenotype, present in the liver in response to chronic DEN+CCl4 treatment. Proteins upregulated or downregulated in platelet-rich plasma from PF4-C3GKO compared to WT mice might regulate the immune response and tumor development. In this regard, enrichment analyses using proteomic data showed changes in several proteins involved in platelet activation and immune response pathways. Additionally, the higher secretion of CD40L by PF4-C3GKO platelets could contribute to their antitumor effect. Therefore, platelet C3G presents antifibrotic and protumor effects in the liver, likely mediated by changes in the immune response. © 2025 The Author(s). The Journal of Pathology published by John Wiley & Sons Ltd on behalf of The Pathological Society of Great Britain and Ireland.

PI3 expression predicts recurrence after chemotherapy with DNA-damaging drugs in gastric cancer.

Despite recent advances in gastric cancer therapy, chemotherapy resistance and lack of methods for selecting combination regimens remain major problems. Organoids, which provide a culture system that more closely resembles tumor cell organization than traditional cell lines, can be established from surgical specimens with a high success rate and are widely used for drug sensitivity assays. In this study, we aimed to identify a novel biomarker for predicting multidrug resistance using gastric cancer organoids (GCOs). We evaluated 5-fluorouracil or oxaliplatin-resistant GCOs to find novel biomarkers that reflect multidrug resistance in gastric cancer. To examine the resistance mechanisms, RNA-sequencing analysis and ex vivo drug sensitivity testing were performed. The association of biomarkers with patient prognosis and chemotherapy efficacy was evaluated using three original cohorts with a total of 230 cases. The results were also validated with two independent public cohorts and single-cell RNA sequence data. Increased expression of peptidase inhibitor 3 (PI3) was detected in all 5-fluorouracil or oxaliplatin-resistant GCOs. Our findings suggest a potential association of PI3 expression with ribosome biosynthesis and RNA metabolism under organoid conditions. We also found that PI3 overexpression promoted 5-fluorouracil/oxaliplatin/cisplatin resistance but not paclitaxel resistance. Immunohistochemical evaluation of PI3 expression revealed that the PI3-positive gastric cancer group had a poorer outcome, especially in terms of time to recurrence. PI3 positivity was also an independent predictor of relapse after chemotherapy with DNA-damaging agents. PI3 promotes DNA-damaging drug resistance through multiple downstream regulations related to RNA and ribosomal metabolism. PI3 may be useful as a biomarker for the therapeutic selection of non-DNA-damaging agents. © 2025 The Author(s). The Journal of Pathology published by John Wiley & Sons Ltd on behalf of The Pathological Society of Great Britain and Ireland.

Redefining phenotypic intratumor heterogeneity of pancreatic ductal adenocarcinoma: a bottom-up approach.

Pancreatic ductal adenocarcinoma (PDAC) tumor interpatient heterogeneity has been well described with two major prognostic subtypes (classical and basal-like). An important intrapatient heterogeneity has been reported but has not yet been studied extensively due to the lack of standardized, reproducible, and easily accessible high-throughput methods. We built an immunohistochemical (IHC) tool capable of differentiating RNA-defined classical and basal-like tumors by selecting relevant antibodies using a multistep process. The successive stages of (i) an in silico selection from a literature review and a bulk transcriptome analysis of 309 PDACs, (ii) a tumor-specific selection from 30 patient-derived xenografts and single-cell data, followed by (iii) the validation on tissue microarrays in 50 PDAC were conducted. We used our final IHC panel on two independent cohorts of resected PDAC (n = 95, whole-slide, n = 148, tissue microarrays) for external validation. After digitization and registration of pathology slides, we performed a tile-based analysis in tumor areas to identify relevant marker combinations. Sequential marker selection led to the following panel: GATA6, CLDN18, TFF1, MUC16, S100A2, KRT17, PanBasal. Four different phenotypes were identified: one classical, one intermediate (KRT17+), and two basal-like (MUC16+ versus S100A2+) with specific biological properties. The presence of a minor basal contingent drastically reduced overall survival [hazard ratio (HR) = 1.90, p = 0.03], even in classical predominant PDACs. Analysis of preneoplastic lesions suggested that pancreatic carcinogenesis might follow a progressive evolution from classical toward a basal through an early intermediate phenotype. In conclusion, our IHC panel redefined and easily assessed the high degree of intra- and intertumoral heterogeneity of PDAC. © 2025 The Author(s). The Journal of Pathology published by John Wiley & Sons Ltd on behalf of The Pathological Society of Great Britain and Ireland.

Comprehensive characterization of micropapillary colorectal adenocarcinoma.

Micropapillary colorectal adenocarcinoma is a morphologic subtype of colorectal cancer (CRC) with insufficiently characterized prognostic significance and biological features. We analyzed the histopathological, immunological, and prognostic features of micropapillary adenocarcinoma in two independent CRC cohorts (N = 1,876). We found that micropapillary adenocarcinomas accounted for 4.9% and 6.4% of CRCs in the two cohorts. A micropapillary growth pattern was associated with advanced stage and lymphovascular invasion (p < 0.001), but also with shorter overall survival independent of these factors and other prognostic parameters (Cohort 1: hazard ratio [HR] 1.76, 95% confidence interval [CI] 1.08-2.87; Cohort 2: HR 1.47, 95% CI 1.08-2.00). Multiplex immunohistochemistry and machine learning-assisted image analysis showed that the micropapillary growth pattern was associated with decreased CD3+ T-cell and CD14+HLA-DR+ monocytic cell densities. Molecular features of micropapillary adenocarcinoma were studied using bioinformatic analyses in The Cancer Genome Atlas (TCGA) cohort (N = 629) and validated with optical genome mapping and immunohistochemistry. These analyses revealed that micropapillary adenocarcinomas frequently present with chromosome region 8q24 copy number gain, TP53 mutation, and overexpression of UPK2, MUC16, and epithelial-mesenchymal transition involved genes, such as L1CAM. These results indicate that micropapillary colorectal adenocarcinoma is an aggressive morphologic subtype of CRC characterized by shorter overall survival, decreased antitumorigenic immune response, and unique molecular features. Our findings support the classification of micropapillary adenocarcinoma as a distinct, high-risk subtype of CRC, which should be systematically evaluated in patient care. © 2025 The Author(s). The Journal of Pathology published by John Wiley & Sons Ltd on behalf of The Pathological Society of Great Britain and Ireland.

Unveiling the intriguing relationship: oncogenic KRAS, morphological shifts, and mutational complexity in pancreatic mucinous cystic neoplasms.

Pancreatic ductal adenocarcinoma (PDAC) often arises from preexisting cystic lesions such as intraductal papillary mucinous neoplasms (IPMN) and mucinous cystic neoplasms (MCN). This study investigated the molecular heterogeneity and mutational landscape of MCN in relation to PDAC, highlighting the significance of KRAS mutations in tumor progression. Utilizing targeted next-generation sequencing on low-grade MCN and invasive PDAC samples, we identified a substantial overlap in mutational profiles, particularly mutations in KRAS, TP53, and FBXW7. Specifically, 69.2% of MCN exhibited somatic mutations, with KRAS mutations being a predominant oncogenic driver. The characterization of mutant versus wildtype KRAS variant allele frequencies (VAF) indicated higher mutation levels in PDAC compared to MCN, suggesting an evolutionary trajectory toward malignancy. Further histological analysis of 12 additional MCN cases revealed significant intratumor heterogeneity, with variant KRAS mutation distributions correlating with distinct cellular morphologies and dysplastic features. Additionally, we explored the potential of liquid biopsies, demonstrating a concordance rate of 71.4% for KRAS mutation detection in circulating tumor DNA (ctDNA) relative to tissue biopsies across cohorts. Our findings underscore the relevance of evaluating KRAS mutations-herein referred to as VAF per microdissected region-as they relate to histopathological markers of dysplasia, contributing to improved stratification of pancreatic lesions and facilitating personalized treatment strategies. In conclusion, this comprehensive analysis of MCN highlights the importance of KRAS as a crucial biomarker for both malignant progression and therapeutic decision-making in pancreatic pathology. Ultimately, our study suggests that characterizing the mutational landscape and histological features of MCN can enhance early detection and intervention strategies for at-risk patients. © 2025 The Author(s). The Journal of Pathology published by John Wiley & Sons Ltd on behalf of The Pathological Society of Great Britain and Ireland.