[Durgical](https://durgical.com/en/) › [DurgiPedia](https://durgical.com/en/durgipedia/) › [General pathology](https://durgical.com/en/general-pathology/) › [White cells, lymph nodes, spleen and thymus](https://durgical.com/en/general-pathology/areas/hematolymphoid/) › Reactive lymphadenitis: the patterns

# Reactive lymphadenitis: the patterns

- Lesion

Lymph nodes swell when they fight. Which part of the node grows tells which arm of immunity is working, and helps rule out lymphoma.

Updated Nov 12, 2026

## Key points

- Follicular hyperplasia: B-cell responses (rheumatoid arthritis, toxoplasmosis, early HIV).
- Paracortical hyperplasia: T-cell responses (viral infections such as mononucleosis, vaccines, drugs like phenytoin).
- Sinus histiocytosis: nodes draining cancers or tissue debris.
- Reactive follicles keep the node architecture, vary in size and shape, have tingible-body macrophages and are BCL2-negative in their germinal centres.
- Stellate necrotizing granulomas with neutrophils: cat-scratch disease (Bartonella).

On this page

- The basics Key points
- What it is
- Structure
- Step by step
- Patterns of reactive lymph node enlargement
- Memory aid
- Elsewhere in DurgiPedia

- Clinical Clinical notes
- In the lab

- Study Test yourself

- Connections Connections

## What it is

Lymph nodes enlarge during infection and immune stimulation. Acute nonspecific lymphadenitis is a tender, swollen node draining an infection, sometimes forming an abscess. Chronic reactive enlargement shows patterns that mirror the immune response: B-cell follicles grow in antibody responses, the T-cell paracortex grows in viral and drug reactions, and the sinuses fill with histiocytes when the node drains a tumour or debris. Granulomas point to mycobacteria, fungi, cat-scratch disease or sarcoidosis.

## Structure

- Acute lymphadenitis: enlarged, red, soft node; neutrophils around follicles and in sinuses; central necrosis when pyogenic bacteria form an abscess.
- Follicular hyperplasia: many large germinal centres with a polarized mix of centroblasts and centrocytes, mitoses and tingible-body macrophages.
- Paracortical hyperplasia: expanded T-cell zones with immunoblasts that may push follicles aside.
- Sinus histiocytosis: distended sinuses packed with large histiocytes and hypertrophic lining cells.

## Step by step

- Antigen or microbes drain to the node through afferent lymphatics.
- Antigen-presenting cells activate the lymphocytes of the matching compartment.
- That compartment expands: follicles for antibody responses, paracortex for T-cell responses, sinuses for clearance of particles.
- Pyogenic bacteria add neutrophils, necrosis and pus; persistent antigens favour granulomas.
- When the stimulus ends, the node shrinks, sometimes leaving fibrosis.

## Patterns of reactive lymph node enlargement

| Pattern | Compartment that expands | Typical causes | Key microscopic clue |
| --- | --- | --- | --- |
| Acute nonspecific lymphadenitis | Whole node, neutrophils | Dental, skin or throat infection draining to the node | Neutrophils, oedema, sometimes abscess |
| Follicular hyperplasia | B-cell follicles | Rheumatoid arthritis, early HIV, syphilis, nonspecific stimulation | Large, irregular germinal centres with tingible-body macrophages |
| [Paracortical hyperplasia](https://durgical.com/en/conditions/infectious-mononucleosis/) | T-cell paracortex | Infectious mononucleosis and other viruses, vaccines, drugs | Immunoblasts filling the interfollicular zone |
| [Toxoplasma lymphadenitis](https://durgical.com/en/conditions/toxoplasmosis/) | Follicles plus small epithelioid clusters | Toxoplasma gondii | Follicular hyperplasia with epithelioid histiocytes near the follicles |
| [Suppurative granulomatous lymphadenitis](https://durgical.com/en/conditions/bartonella-infections/) | Granulomas with central neutrophils | Cat-scratch disease (Bartonella henselae) | Stellate necrotizing granulomas |
| [HIV lymphadenopathy](https://durgical.com/en/conditions/hiv-infection-and-aids/) | Follicles, then their collapse | Untreated HIV infection | Florid follicles early, burnt-out depleted follicles late |

## Clinical notes

- Tender, warm nodes suggest acute infection; hard, fixed, painless nodes suggest cancer.
- Persistent generalized lymphadenopathy is common in HIV; in Colombia tuberculosis and histoplasmosis are frequent granulomatous causes.
- Chronic lymphadenitis is common in inguinal and axillary nodes, which drain frequent minor skin injuries.

## In the lab

- Excisional biopsy keeps the architecture, which matters more than single cells in separating reactive from malignant nodes.
- Immunostaining for BCL2 and clonality studies help when follicles look suspicious.

## Memory aid

Follicles for antibodies, paracortex for viruses, sinuses for the drain, granulomas for the stubborn.

## Test yourself

Think of the answer, then tap the question to see it.

## Which node compartment expands in infectious mononucleosis?

The T-cell paracortex, filled with activated immunoblasts.

## Which three features favour reactive follicular hyperplasia over follicular lymphoma?

Preserved architecture, follicles of varying size and shape with tingible-body macrophages and mitoses, and BCL2-negative germinal centres.

## What kind of granuloma does cat-scratch disease produce?

Stellate necrotizing granulomas with central neutrophils (suppurative granulomatous lymphadenitis).

[Add to my cards (3)](https://durgical.app/estudiar/?add=/en/general-pathology/reactive-lymphadenitis-the-patterns/)

[More Pathology questions →](https://durgical.com/en/practice/?f=pathology)

## Elsewhere in DurgiPedia

- [Lymph node and spleen under the microscope](https://durgical.com/en/histology/lymph-node-and-spleen-under-the-microscope/)
- [Lymph node: cortex, paracortex, medulla](https://durgical.com/en/immunology/lymph-node-cortex-paracortex-medulla/)
- [B-cell activation, class switching and affinity maturation](https://durgical.com/en/immunology/b-cell-activation-class-switching-and-affinity-maturation/)
- [Primary and secondary lymphoid organs](https://durgical.com/en/immunology/primary-and-secondary-lymphoid-organs/)

## Connections

## Related 5

- [Granulomatous inflammation: caseating vs non-caseating, the causes to know](https://durgical.com/en/general-pathology/granulomatous-inflammation-caseating-vs-non-caseating-the-causes-to-know/)
- [Patterns of acute inflammation: serous, fibrinous, purulent, abscess, ulcer](https://durgical.com/en/general-pathology/patterns-of-acute-inflammation-serous-fibrinous-purulent-abscess-ulcer/)
- [Follicular lymphoma](https://durgical.com/en/general-pathology/follicular-lymphoma/)
- [Hodgkin lymphoma](https://durgical.com/en/general-pathology/hodgkin-lymphoma/)
- [Granulomatous pneumonia: tuberculosis and endemic fungi](https://durgical.com/en/general-pathology/granulomatous-pneumonia-tuberculosis-and-endemic-fungi/)

## Related conditions 10

- [Cervical lymphadenopathy](https://durgical.com/en/conditions/cervical-lymphadenopathy/)
- [Bartonella infections (cat-scratch disease, Carrion disease)](https://durgical.com/en/conditions/bartonella-infections/)
- [Toxoplasmosis](https://durgical.com/en/conditions/toxoplasmosis/)
- [Infectious mononucleosis](https://durgical.com/en/conditions/infectious-mononucleosis/)
- [Castleman disease](https://durgical.com/en/conditions/castleman-disease/)
- [HIV infection and AIDS](https://durgical.com/en/conditions/hiv-infection-and-aids/)
- [Tuberculosis](https://durgical.com/en/conditions/tuberculosis/)
- [Sarcoidosis](https://durgical.com/en/conditions/sarcoidosis/)
- [Rheumatoid arthritis](https://durgical.com/en/conditions/rheumatoid-arthritis/)
- [Non-Hodgkin lymphoma](https://durgical.com/en/conditions/non-hodgkin-lymphoma/)

## Microorganisms 4

- [Bartonella](https://durgical.com/en/microbiology/bartonella/)
- [Toxoplasma gondii](https://durgical.com/en/microbiology/toxoplasma-gondii/)
- [Epstein–Barr virus](https://durgical.com/en/microbiology/epstein-barr-virus/)
- [Mycobacterium tuberculosis](https://durgical.com/en/microbiology/mycobacterium-tuberculosis/)

[← All of general pathology](https://durgical.com/en/general-pathology/)

Educational content on the mechanisms of disease; not a diagnostic or treatment guide and no substitute for a health professional's advice. No doses are given.

Sources: [Lymphadenitis: MedlinePlus Medical Encyclopedia](https://medlineplus.gov/ency/article/001301.htm) (MedlinePlus, US National Library of Medicine, 2026); [Lymphadenopathy](https://www.ncbi.nlm.nih.gov/books/NBK513250/) (StatPearls (NCBI Bookshelf), 2026).

## **Spotted a mistake?** We are always improving for the community. Tell us what is wrong and our team will review it. Report a mistake

Representative model, for educational purposes only.

---
Source: https://durgical.com/en/general-pathology/reactive-lymphadenitis-the-patterns/
License: CC BY 4.0 (https://creativecommons.org/licenses/by/4.0/). Cite as: DurgiPedia (durgical.com), https://durgical.com/en/general-pathology/reactive-lymphadenitis-the-patterns/