Tertiary Lymphoid Structures (TLS) in Cancer: Unlocking New Insights into Tumor Immunity and Immunotherapy Response

 

Tertiary Lymphoid Structures in Cancer: New Frontiers in Tumor Immunity and Immunotherapy

Introduction

Cancer is not driven by tumor cells alone. The surrounding tumor microenvironment contains immune cells, blood vessels, stromal cells, signaling molecules, and extracellular structures that can strongly influence how a tumor grows and how it responds to treatment. Among the emerging areas of cancer immunology, tertiary lymphoid structures (TLS) have attracted increasing attention because of their potential role in organizing local immune responses against tumors.

Tertiary lymphoid structures are organized collections of immune cells that develop in tissues outside conventional lymphoid organs such as lymph nodes and the spleen. Unlike normal secondary lymphoid organs, TLS are generally formed in response to chronic inflammation, infection, autoimmune processes, or cancer. Within tumors, these structures can create specialized local environments where immune cells interact, recognize antigens, and coordinate anti-tumor responses.

Research into TLS in cancer is particularly relevant to modern immuno-oncology because some studies have associated the presence, organization, and maturation of TLS with immune activity and responses to certain cancer immunotherapies. However, TLS are biologically diverse, and their significance can vary according to tumor type, location, maturity, cellular composition, and treatment context.

Understanding how TLS develop and function could therefore provide new insights into tumor immunity, cancer biomarkers, and personalized approaches to immunotherapy.

 

What Are Tertiary Lymphoid Structures?

Tertiary lymphoid structures are organized immune-cell aggregates that form within non-lymphoid tissues under conditions of persistent immune stimulation.

They are sometimes described as ectopic lymphoid structures because they resemble certain features of conventional lymphoid tissues but develop at sites where lymphoid organs are normally absent.

TLS can contain several types of immune cells, including:

• B cells
• T cells
• Dendritic cells
• Antigen-presenting cells
• Plasma cells
• Stromal cells
• Specialized endothelial cells

Their organization can vary considerably. Some TLS may consist primarily of loosely organized immune-cell aggregates, while more mature structures can demonstrate distinct B-cell and T-cell zones and other characteristics resembling secondary lymphoid organs.

In cancer, TLS can develop within or around tumors and may influence communication between different components of the immune system.

 

How Do TLS Develop in Tumors?

TLS formation is associated with persistent inflammatory signaling within tissues.

Several molecular and cellular processes may contribute to their development. Chemokines and cytokines can recruit immune cells to the tumor microenvironment and help organize them into more structured communities.

Important signaling molecules associated with lymphoid organization include chemokines involved in the recruitment of B cells and T cells, as well as factors that influence lymphoid stromal-cell development and vascular specialization.

The process can involve:

1. Recruitment of immune cells into the tumor microenvironment.
2. Activation of local inflammatory pathways.
3. Organization of B cells and T cells.
4. Development of supporting stromal networks.
5. Formation of specialized blood-vessel structures.
6. Progressive maturation of the lymphoid-like organization.

The exact mechanisms are still being investigated, and TLS formation is not identical across all cancers.

 

Cellular Composition of Tumor-Associated TLS

The biological activity of a TLS depends partly on the types of cells it contains and how those cells are organized.

B Cells

B cells are an important component of many TLS. They can participate in antigen recognition, antibody production, and communication with other immune cells.

In some mature TLS, B cells can organize into structures resembling germinal centers, where B-cell activation and maturation may occur.

T Cells

T cells contribute to cellular immune responses against malignant cells. Different T-cell populations may be present within or around TLS, including helper T cells and cytotoxic T cells.

Their interaction with antigen-presenting cells and B cells can contribute to coordinated anti-tumor immunity.

Dendritic Cells

Dendritic cells play an important role in antigen presentation and T-cell activation. Their presence within organized immune structures may help facilitate communication between tumor-associated antigens and adaptive immune responses.

Plasma Cells

Some mature TLS contain plasma cells capable of producing antibodies. These antibodies may contribute to immune recognition of tumor-associated targets, although their precise contribution can vary between cancer types.

Stromal Cells

Stromal components help provide the structural framework required for organization of immune cells. Stromal signaling can also influence the recruitment and positioning of lymphocytes.

 

TLS and the Tumor Immune Microenvironment

The tumor immune microenvironment is highly complex. Some tumors contain substantial immune-cell infiltration, whereas others have limited immune activity.

TLS may represent specialized locations where immune cells can interact more efficiently.

Rather than viewing immune cells as randomly distributed throughout a tumor, TLS research emphasizes the importance of immune-cell organization and spatial relationships.

This distinction is important because two tumors could contain similar numbers of immune cells but demonstrate different patterns of immune organization and potentially different biological behavior.

TLS therefore provide an additional perspective for understanding the spatial architecture of tumor immunity.

 

Mature and Immature TLS

Not all TLS have the same biological characteristics.

Researchers commonly distinguish between less organized or immature TLS and more developed structures.

Immature TLS

Immature structures may contain clusters of immune cells without clearly defined organization. They can still indicate local immune activation but may not have the complete functional characteristics associated with mature TLS.

Mature TLS

More mature TLS can demonstrate:

• Organized B-cell areas
• T-cell-rich regions
• Follicle-like structures
• Germinal-center-like organization
• Specialized vascular features
• More complex interactions between immune-cell populations

The degree of TLS maturation may therefore be important when studying their relationship with treatment response.

 

TLS as Potential Biomarkers in Cancer

One of the major research interests surrounding TLS is their potential use as biomarkers of immune activity and treatment response.

Traditional cancer biomarkers often focus on molecular characteristics such as gene mutations, protein expression, or tumor mutational features. TLS provide another potential layer of information by examining the organization of the immune environment.

Researchers are investigating whether:

• TLS presence correlates with immune activation.
• TLS maturity provides additional predictive information.
• TLS location within or around tumors affects their biological significance.
• TLS characteristics correlate with response to immunotherapy.
• TLS can complement existing biomarkers.

However, TLS should not currently be treated as a universal predictor of treatment response. Their interpretation depends on tumor type, methodology, clinical context, and the characteristics of the structures being measured.

 

TLS and Cancer Immunotherapy

Immune checkpoint inhibitors have transformed treatment for several cancers by enabling anti-tumor immune responses that may otherwise be suppressed.

The response to immunotherapy, however, varies considerably among patients.

This has encouraged researchers to investigate whether the organization of the tumor immune microenvironment can help explain differences in treatment response.

TLS are of particular interest because they may provide a local environment where immune-cell activation and communication occur.

Studies across several tumor types have reported associations between TLS characteristics and immune checkpoint inhibitor responses. However, these findings do not mean that the presence of TLS alone guarantees therapeutic benefit.

Instead, TLS may eventually become one component of a broader biomarker framework combining tumor genomics, immune-cell composition, spatial organization, and clinical characteristics.

 

Why Spatial Organization Matters

Cancer research has increasingly moved beyond measuring how many immune cells are present toward understanding where those cells are located and how they interact.

Spatial biology technologies can help researchers investigate:

• The location of immune-cell populations.
• Relationships between B cells and T cells.
• Immune-cell proximity to malignant cells.
• Organization of tumor-associated structures.
• Cellular neighborhoods within tumors.
• Changes in immune architecture following treatment.

This makes TLS particularly relevant to emerging fields such as spatial transcriptomics, spatial proteomics, multiplex imaging, and digital pathology.

Rather than analyzing tumor biology only as an average molecular signal, spatial approaches can reveal the physical organization of cellular interactions.

 

TLS in Different Cancer Types

TLS have been investigated across a wide range of malignancies.

Research has examined their potential significance in cancers including:

• Melanoma
• Lung cancer
• Breast cancer
• Colorectal cancer
• Gastric cancer
• Ovarian cancer
• Pancreatic cancer
• Renal cancer
• Sarcomas
• Head and neck cancers

The relationship between TLS and clinical outcomes is not necessarily identical across these diseases.

Differences in tumor biology, immune environment, treatment strategies, TLS maturity, and measurement techniques can all influence research findings.

Therefore, cancer-specific investigation remains important.

 

TLS and Precision Oncology

Precision oncology traditionally focuses on matching treatments to the molecular characteristics of an individual patient's tumor.

TLS research could potentially expand this concept by incorporating immune architecture into treatment planning.

Future precision oncology models may combine:

• Genomic alterations
• Transcriptomic profiles
• Proteomic information
• Immune-cell composition
• Tumor mutational characteristics
• Spatial immune organization
• TLS presence and maturity
• Clinical and treatment data

Such integrated models could provide a more comprehensive representation of tumor biology.

However, clinical implementation will require standardized methods and prospective validation.

 

Detecting TLS in Tumor Samples

TLS can be evaluated using several approaches.

Histopathology

Traditional tissue staining can help identify organized immune-cell aggregates and their structural characteristics.

Immunohistochemistry

Multiple immune markers can be used to distinguish B cells, T cells, dendritic cells, endothelial cells, and other components.

Multiplex Imaging

Multiplex technologies allow researchers to visualize several proteins or cellular markers simultaneously and study their spatial relationships.

Digital Pathology

Artificial intelligence and image-analysis systems may assist researchers in identifying and quantifying TLS features across large numbers of tissue samples.

Spatial Omics

Spatial transcriptomics and spatial proteomics can provide molecular information while retaining information about where specific signals occur within tissue.

These technologies could make TLS assessment increasingly quantitative and reproducible.

 

Artificial Intelligence and TLS Research

Artificial intelligence may contribute to the analysis of tumor immune architecture.

Digital pathology platforms can potentially analyze large tissue images and identify patterns that are difficult to quantify manually.

AI-assisted approaches could support:

• TLS detection
• Classification of TLS maturity
• Immune-cell identification
• Spatial relationship analysis
• Quantification of cellular neighborhoods
• Correlation with clinical outcomes

However, AI models require high-quality annotated datasets and external validation. Differences in tissue preparation, staining methods, scanners, and patient populations can affect model performance.

Therefore, AI should complement expert pathology and clinical interpretation rather than replace them.

 

TLS and Treatment Resistance

Cancer treatment resistance remains a major challenge in oncology.

Some tumors demonstrate limited immune activity, while others develop mechanisms that suppress immune responses over time.

Understanding TLS may provide another way to investigate why some tumors maintain coordinated immune activity while others do not.

Researchers are examining whether manipulating immune-cell recruitment, vascular features, inflammatory signaling, or stromal organization could influence TLS development.

This raises an important research question: Can TLS formation or maturation be therapeutically influenced?

Potential strategies remain under investigation, and more clinical evidence is needed before TLS-directed approaches can become established treatment strategies.

 

Can TLS Be Therapeutically Created or Enhanced?

The possibility of inducing or enhancing TLS is an emerging area of cancer research.

Researchers are investigating whether immune-stimulating approaches could promote the development of more organized anti-tumor immune environments.

Potential areas of investigation include:

• Chemokine modulation
• Cytokine-based approaches
• Immune checkpoint inhibition
• Cancer vaccines
• Radiation therapy
• Combination immunotherapy
• Targeted immune activation
• Stromal and vascular modulation

The objective is not simply to increase inflammation but potentially to create a coordinated immune environment capable of supporting sustained anti-tumor activity.

This field remains experimental, and the safety and clinical effectiveness of TLS-targeting approaches require further investigation.

 

Challenges in TLS Research

Despite growing interest, several challenges remain.

Lack of Universal Definitions

Different studies may use different criteria to identify TLS and classify their maturity.

Sampling Limitations

A biopsy represents only a portion of a tumor. TLS distribution may vary considerably within the same tumor.

Cancer-Specific Differences

The biological significance of TLS may differ between cancer types.

Methodological Variation

Histology, immunohistochemistry, multiplex imaging, and spatial technologies can produce different types of information.

Need for Standardization

Consistent definitions, scoring systems, and detection methods are necessary for comparing results between studies.

Limited Prospective Evidence

Many observations are based on retrospective or exploratory research. Prospective clinical validation remains important.

 

The Future of TLS Research in Oncology

Future TLS research is likely to become increasingly integrated with spatial biology, artificial intelligence, immunology, and precision medicine.

Researchers may combine TLS information with genomic and molecular data to create more detailed immune profiles of individual tumors.

Potential future developments include:

• Automated TLS detection using AI.
• Standardized TLS scoring systems.
• Integration of TLS with spatial omics.
• TLS-based biomarker panels.
• Patient-specific immune architecture mapping.
• Investigation of therapies that promote beneficial TLS formation.
• Integration of TLS into clinical trial design.
• Combination of TLS analysis with existing immunotherapy biomarkers.

The ultimate goal is to understand how the organization of the tumor immune environment contributes to disease progression and treatment response.

 

Why Tertiary Lymphoid Structures Matter for Cancer Research

TLS represent an important shift in the way researchers think about tumor immunity.

Cancer immunology is no longer focused only on whether immune cells are present or absent. Increasing attention is being placed on how immune cells are organized, where they interact, and how these interactions influence anti-tumor responses.

TLS provide a model for studying this organization.

Their potential importance extends across cancer immunology, biomarker discovery, digital pathology, spatial biology, precision oncology, and immunotherapy research.

As technologies for analyzing tumor architecture continue to improve, TLS may become increasingly useful for understanding individual differences in cancer biology.

 

Conclusion

Tertiary lymphoid structures in cancer represent an emerging area of research connecting tumor biology, immune organization, spatial biology, and precision oncology.

These organized immune structures can contain B cells, T cells, dendritic cells, stromal cells, and other immune components that may contribute to local anti-tumor responses. Research has suggested associations between TLS characteristics and outcomes or responses to immunotherapy in several cancer types, although their clinical interpretation remains dependent on tumor type, TLS maturity, location, detection methods, and treatment context.

Advances in multiplex imaging, digital pathology, spatial transcriptomics, spatial proteomics, and artificial intelligence are creating new opportunities to study TLS at much greater resolution.

In the future, TLS assessment may become part of broader immune and molecular profiling strategies designed to better characterize individual tumors. Continued research and prospective clinical validation will be essential to determine how TLS information can be translated into reliable biomarkers and therapeutic strategies.

The growing understanding of TLS highlights an important principle in modern oncology: tumor biology is influenced not only by cancer cells themselves, but also by the complex and highly organized immune environment surrounding them.

 

WCOCC-2026: Advancing the Future of Oncology Research

The World Conference on Oncology & Cancer Care (WCOCC-2026) brings together oncologists, cancer researchers, clinicians, healthcare professionals, academics, and industry experts to discuss emerging developments in cancer research, diagnosis, treatment, precision oncology, immunotherapy, and cancer care.

WCOCC-2026
November 19–21, 2026 | Tokyo, Japan

Researchers and healthcare professionals are invited to submit their latest research, clinical findings, innovative approaches, and scientific work for presentation and discussion at the conference.

Frequently Asked Questions (FAQs)

1. What are tertiary lymphoid structures in cancer?

Tertiary lymphoid structures are organized collections of immune cells that develop in non-lymphoid tissues, including tumors, in response to chronic immune stimulation and inflammation.

2. What cells are found in TLS?

TLS may contain B cells, T cells, dendritic cells, plasma cells, stromal cells, and specialized vascular components.

3. Are TLS the same as lymph nodes?

No. TLS develop locally within non-lymphoid tissues and are not conventional lymph nodes. However, mature TLS can share some structural and functional characteristics with secondary lymphoid organs.

4. Why are TLS important in cancer?

TLS may provide organized environments for immune-cell communication and activation and are being investigated for their potential relationship with anti-tumor immunity and immunotherapy response.

5. Can TLS predict immunotherapy response?

Research has reported associations between certain TLS characteristics and immunotherapy response in several cancers. However, TLS are not a universal predictor, and their clinical utility requires further validation.

6. What is the difference between mature and immature TLS?

Immature TLS are generally less organized, whereas mature TLS can contain more distinct B-cell and T-cell regions and may demonstrate germinal-center-like structures and specialized vascular features.

7. Can TLS be detected using pathology?

Yes. Histopathology, immunohistochemistry, multiplex imaging, and digital pathology can be used to identify and characterize TLS.

8. How can artificial intelligence help TLS research?

AI can assist with tissue-image analysis, immune-cell identification, TLS detection, spatial analysis, and quantitative assessment of tissue architecture.

9. Are TLS found in all cancers?

TLS have been reported in multiple cancer types, but their presence, organization, and biological significance can vary between tumors and individual patients.

10. Can TLS be used in precision oncology?

TLS may eventually contribute to precision oncology by adding information about tumor immune architecture to genomic, molecular, and clinical profiles. More validation is required before widespread clinical implementation.

11. Can researchers manipulate TLS?

Researchers are investigating approaches that could influence TLS formation or maturation, including immune stimulation, chemokine modulation, radiation, vaccines, and combination immunotherapy. These approaches remain under investigation.

12. What technologies are advancing TLS research?

Important technologies include multiplex imaging, digital pathology, spatial transcriptomics, spatial proteomics, single-cell analysis, and artificial intelligence.

13. Why is spatial biology important for TLS?

Spatial biology helps researchers understand not only which immune cells are present but also where they are located and how they interact within the tumor microenvironment.

14. What is the future of TLS research?

Future research may focus on standardized TLS classification, AI-assisted detection, spatial immune profiling, biomarker development, and potential TLS-targeted therapeutic strategies.

15. Where can researchers discuss emerging oncology research?

Researchers can participate in scientific conferences such as the World Conference on Oncology & Cancer Care (WCOCC-2026) to present research and exchange knowledge with professionals working across oncology and cancer care.