This Week in Pathology — Jun 16, 2026

Welcome to This Week in Pathology. This week we're covering 9 notable papers spanning innovations in cancer diagnostics, new insights into CNS pathology, and the mechanisms driving disease from inflammatory bowel disease to rare genetic disorders. Let's dive in.

We begin with innovations in cancer diagnostics and monitoring, where several papers propose refining how we screen, diagnose, and follow our patients. In The American Journal of Surgical Pathology, a study makes a strong case for universal screening for mismatch repair deficiency in specific sarcoma subtypes [3]. Investigators analyzed 39 mismatch repair-deficient sarcomas and found enrichment in pleomorphic rhabdomyosarcoma, uterine leiomyosarcoma, and unclassified or undifferentiated pleomorphic sarcomas. Specifically, they found that 5.6% of uterine leiomyosarcomas and 2.3% of undifferentiated pleomorphic sarcomas in their database were mismatch repair-deficient. Based on these findings, the authors propose universal immunohistochemistry screening for these specific sarcoma types, as well as for any sarcoma in a patient with a history suggestive of Lynch syndrome. This could identify patients who may benefit from immune checkpoint inhibition and also uncover previously undiagnosed Lynch syndrome. Interestingly, they also identified a specific histologic subtype of undifferentiated sarcoma, which they termed 'distinctive lobulated inflammatory sarcoma,' that was associated with an excellent prognosis and response to immunotherapy. Shifting from immunohistochemistry to artificial intelligence, a paper in The American Journal of Pathology explores the potential of deep learning to infer molecular status directly from routine histology slides [4]. Researchers developed a Vision Transformer-based model to predict TP53 mutation status from whole slide images across 32 different solid tumor types. The model achieved an area under the receiver operating characteristic curve of 0.766 on an independent validation set, demonstrating that reproducible morphologic correlates of TP53 alterations do exist across various cancers. While the model could also predict cancer type and TP53 expression levels, the authors note that its ability to predict prognostic risk was limited. Finally, in the realm of post-treatment monitoring, a study in Science Translational Medicine validates a highly sensitive HPV whole-genome sequencing assay for detecting minimal residual disease in patients with HPV-positive head and neck cancer treated with surgery [9]. This assay, called HPV-DeepSeek, was shown to be a stronger predictor of recurrence than standard clinicopathologic criteria. It detected circulating tumor HPV DNA after treatment, which was associated with significantly worse disease-free and overall survival. Critically, molecular recurrence was identified up to 17.5 months earlier than clinical recurrence, suggesting this tool could substantially improve postoperative risk stratification and guide decisions on adjuvant therapy.

Next, we turn to the central nervous system, with two papers focusing on cerebrospinal fluid analysis. For decades, CSF cytology has lacked a standardized reporting system, leading to diagnostic variability. A study in Cancer Cytopathology addresses this by applying The International System for Serous Fluid Cytopathology to over 850 CSF cases [2]. By classifying cases into categories like 'negative for malignancy', 'atypia of uncertain significance', 'suspicious for malignancy', and 'malignant', they were able to establish a clear risk of malignancy for each category, which was 4.5% for atypia and 66.7% for suspicious cases. The system achieved a diagnostic accuracy of 99%, and when combined with flow cytometry, it helped reduce the number of indeterminate diagnoses, particularly in cases with a history of hematologic malignancy. The authors conclude that adopting this system can standardize terminology and improve diagnostic performance. Also in the CNS, a paper in Cell investigates the immunologic factors that determine response to CAR T-cell therapy in recurrent glioblastoma [1]. While the infused CAR T-cells became activated in all patients, clinical outcomes diverged dramatically. The study, which performed in-depth profiling of CSF and tumor samples, revealed that the patient's own endogenous immune system was the critical factor. Responders were characterized by an expansion of cytotoxic natural killer cells in the CSF. In contrast, non-responders showed an expansion of regulatory T-cells and had an abundance of immunosuppressive myeloid cells at baseline. This finding suggests that the success of CAR T-cell therapy in solid tumors like glioblastoma may depend on combination strategies that modulate the host immune environment to favor a cytotoxic response.

Our final theme covers novel disease mechanisms and therapeutics. In The New England Journal of Medicine, researchers identified neutralizing autoantibodies against interleukin-10 in about 3.5% of a large cohort of patients with inflammatory bowel disease; these autoantibodies were absent in over a thousand controls [8]. Functionally, these antibodies were shown to impair IL-10 signaling, resulting in an exaggerated proinflammatory cytokine response in vitro. The most significant finding was a powerful association between these autoantibodies and the HLA-DRB1*01:03 allele, which is the strongest known genetic risk factor for ulcerative colitis. This provides a compelling mechanistic link between a key genetic risk factor and a specific immunophenotype. From immunology to fundamental biology, a paper in Nature reveals a surprising role for the deacetylase SIRT7 in safeguarding the female X chromosome [5]. Investigating sex differences in Sirt7 knockout mice, the team found that SIRT7 preferentially localizes to sex chromosomes. In females, its loss disrupts X-chromosome inactivation and causes the active X chromosome to become disorganized, prone to DNA damage, and overexpressed. This leads to a genome-wide imbalance, providing a potential explanation for the sex-biased effects observed in SIRT7 biology. On the therapeutic front, another paper in The New England Journal of Medicine reports on a gene therapy trial for X-linked retinoschisis [7]. Twelve patients received a single subretinal injection of an AAV8 vector carrying the human RS1 gene. The treatment was found to be safe, with no grade 3 or higher adverse events reported over 52 weeks. Treated eyes showed significant structural improvements, with complete closure of the macular schisis cavity seen in all patients. Functionally, treated eyes had a mean improvement in best corrected visual acuity of 10.8 letters, compared to just 2.4 letters in untreated eyes. Finally, a study in Science Translational Medicine describes a promising therapeutic strategy against the highly pathogenic Nipah and Hendra viruses [10]. Scientists developed a cocktail of human monoclonal antibodies targeting two different viral proteins: the fusion protein and the receptor binding protein. This dual-targeting approach not only provided cross-species neutralization but was also more resilient to escape mutants compared to a single antibody. The cocktail gave complete protection against lethal Nipah virus challenge in hamsters, even when treatment was delayed, establishing a strong candidate for next-generation countermeasures against these deadly emerging viruses.

If you only have time for one paper this week, make it the study in The American Journal of Surgical Pathology on mismatch repair deficiency in sarcomas [3]. It provides strong evidence to support a change in practice, recommending universal immunohistochemistry screening for specific, readily identifiable sarcoma subtypes, which could directly impact patient care by identifying Lynch syndrome and guiding immunotherapy.

Here are the key takeaways from this week in Pathology: First, consider implementing universal mismatch repair screening via immunohistochemistry for pleomorphic rhabdomyosarcoma, uterine leiomyosarcoma, and undifferentiated sarcomas to identify candidates for immunotherapy and screen for Lynch syndrome [3]. Second, for patients with HPV-positive head and neck cancer, a new highly sensitive ctDNA assay can detect minimal residual disease after surgery far earlier than clinical recurrence, offering a powerful tool for risk stratification and potentially guiding adjuvant therapy decisions [9]. Third, adopting The International System for Serous Fluid Cytopathology for CSF specimens can standardize reporting, improve diagnostic accuracy, and provide clear risk stratification for malignancy [2]. Fourth, in glioblastoma, the success of CAR T-cell therapy appears to depend heavily on the patient's endogenous immune response, suggesting that future strategies may need to combine CAR T-cells with therapies that modulate host immunity, such as boosting NK cells or inhibiting regulatory T cells [1]. And finally, a subset of inflammatory bowel disease patients, particularly those with the HLA-DRB1*01:03 allele, have neutralizing autoantibodies to IL-10, identifying a potential therapeutic target and a distinct disease endotype [8].

That's your roundup for This Week in Pathology. The full transcript and references are available on the episode page in your AudioScholar library. This is an AI-curated summary — for clinical decisions, always consult primary sources and current guidelines. See you next week.

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This is an automated summary generated by artificial intelligence, which can make mistakes. Always review the original source materials.