Pathologists’ examinations of tissue samples from skin cancer tumors have taken a significant leap forward through the assistance of artificial intelligence (AI). A groundbreaking study led by Karolinska Institutet, in collaboration with Yale University, reveals that using AI to aid in the assessment of tumor-infiltrating lymphocytes (TILs) enhances both the consistency and accuracy of pathological diagnoses. This advancement holds promise for improving the prognostic evaluation of malignant melanoma patients, potentially informing more effective treatment strategies in the near future.

Tumor-infiltrating lymphocytes are a crucial biomarker within several cancer types, particularly malignant melanoma, the deadliest form of skin cancer. These immune cells infiltrate the tumor microenvironment and play an essential role in modulating the body’s immune response against tumor cells. Traditionally, pathologists estimate the density and localization of TILs by visually examining stained tissue sections under microscopy. This information serves two main clinical purposes: assisting in accurate diagnosis and providing insight into how aggressive or advanced a patient’s cancer is likely to be. However, manual estimations are inherently subjective and prone to inter-observer variability, which can limit the reproducibility and reliability of prognostic assessments.

The research team thus embarked on a study to evaluate how an AI-based tool designed to quantify TILs could influence pathological evaluations. The AI was trained to analyze digitized images of stained melanoma tissue sections, automatically identifying and counting immune cells within or adjacent to the tumor. The study enrolled 98 participants, comprising pathologists and other researchers with experience in pathology image assessments. These individuals were split into two groups. The control group consisted exclusively of experienced pathologists who performed assessments in the traditional manner without AI assistance. The experimental group included pathologists and other research professionals who analyzed the same images but with the benefit of AI-generated quantifications of TIL presence.

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Each participant reviewed 60 digital tissue images from melanoma patients, with all cases retrospectively selected, meaning patient outcomes and treatment histories were already known but blinded to the assessors. The core aim was to compare the reproducibility between human-only and AI-assisted assessments, as well as to determine which method more accurately correlated with the true clinical outcomes. Remarkably, the results demonstrated the AI-supported group’s assessments to be not only more reproducible—showing significantly less variability between different evaluators—but also more predictive of patient prognoses. This suggests that integrating AI into pathological workflows can substantially augment the diagnostic precision in melanoma cases.

Reproducibility in pathological assessments is a critical factor directly linked to medical safety and treatment planning. Variations in TIL quantification by different pathologists have historically posed challenges for consistent prognoses, which could inadvertently affect decisions regarding the aggressiveness of therapy. By leveraging AI to reduce this variability, healthcare providers may be able to rely on more standardized and objective biomarker evaluations, ultimately leading to more personalized and effective patient management strategies.

Beyond reproducibility, the study’s retrospective design allowed for comparison against actual patient outcomes that had been previously documented. The AI-assisted assessments showed a higher concordance with these outcomes, indicating better clinical validity. This is a vital indicator of the AI tool’s potential utility in real-world clinical settings. Such AI-driven analyses could assist pathologists by highlighting areas of interest within tissue samples or by providing quantitative data that substantiate their qualitative judgments.

Balazs Acs, associate professor at the Department of Oncology-Pathology at Karolinska Institutet and a clinical pathologist involved in the study, remarked on the clinical implications of this breakthrough. He noted that understanding the severity of a patient’s melanoma through tissue analysis is fundamental for guiding treatment—it informs decisions about how aggressively a tumor should be managed. The new AI tool offers a robust means to quantify the TIL biomarker, representing an important step toward integrating AI into routine diagnostic pathology.

While the results are highly encouraging, the researchers emphasize that additional studies are necessary to confirm the clinical utility and safety of this AI tool before it becomes a standard component of pathology practice. These validation studies would verify its performance across diverse patient populations, institutions, and varied clinical scenarios. Nonetheless, the findings mark an important milestone in the convergence of artificial intelligence and medical diagnostics, with the potential to reshape how oncologists and pathologists approach melanoma prognostication.

The careful collaboration of multidisciplinary researchers, including computer scientists, pathologists, and clinicians, played an instrumental role in successfully developing this AI technology. The study demonstrates the feasibility of deploying AI in complex medical tasks and underscores the importance of human-AI collaboration rather than full automation. The AI tool acts as an adjunct, assisting experts to reach more accurate and repeatable decisions that can benefit patient care.

Funding for this study was provided by prestigious bodies including the Swedish Society for Medical Research, Region Stockholm, and several grants from the U.S. National Institutes of Health. These investments underscore the global importance of advancing AI applications in cancer diagnostics and support for cutting-edge innovations in pathology.

As the medical community continues to explore the intersection of artificial intelligence and histopathology, studies such as this highlight the transformative potential of integrating advanced computational tools into clinical workflows. With further validation, AI-assisted pathology could soon become a vital component in the diagnosis and treatment monitoring not only for melanoma but also for other cancers where immune cell infiltration is a key prognostic factor.

In sum, this landmark study provides compelling evidence that AI-supported analysis of tumor-infiltrating lymphocytes enhances both the precision and reproducibility of skin cancer pathology. Such innovations pave the way for more accurate prognostic assessments, ultimately improving personalized therapy approaches for patients afflicted with malignant melanoma.

Subject of Research: Not applicable
Article Title: Analytical and Clinical Validity of Pathologist-read versus AI-Driven Assessments of Tumor-Infiltrating Lymphocytes in Melanoma: A Multi-Operator and Multi-Institutional Study
News Publication Date: 3-Jul-2025
Web References: http://dx.doi.org/10.1001/jamanetworkopen.2025.18906
References: Aung TN, Liu M, Su D, Shafi S, et al. Analytical and Clinical Validity of Pathologist-read versus AI-Driven Assessments of Tumor-Infiltrating Lymphocytes in Melanoma: A Multi-Operator and Multi-Institutional Study. JAMA Network Open, 2025.
Image Credits: Photo: Niklas Elmehed
Keywords: Artificial intelligence, Skin cancer, Tumor growth

Tags: accuracy in tissue sample analysisadvancements in cancer researchAI in pathologyAI tools in healthcareAI-enhanced medical diagnosticsCancer Treatment Strategiesimmune response in tumorsinter-observer variability in pathologymalignant melanoma prognosispathologist collaboration with AIskin cancer diagnosistumor-infiltrating lymphocytes assessment