Lymphadenitis. Types of lymphadenitis according to histological characteristics
Lymphadenitis is inflammation of the lymph nodes, it is a type of lymphadenopathy. Lymphadenitis occurs thanks to exposure to bacteria, viruses or fungi, causing swelling of the lymph node. Symptoms may include redness, swelling, tenderness of node, or solidity of the node. They can feel soft and fluctuant if an abscess has formed.
There are two main types:
- Localised lymphadenitis
- Generalised lymphadenitis (2+)
Can also be described based on onset:
- Acute
- Chronic
Macroscopically, all nodes just appear enlarged, chronic form may have thickened capsule, acute form may have suppuration leading to necrosis and abscess. Microscopically, acute form shows sinus dilation, accumulation of neutrophils, vascular dilation and edema, if bacterial with suppurative inflammation and necrotizing inflammation in bubonic plague. Microscopically in chronic form, observe follicular hyperplasia, increased immunoblasts, plasma cells and presence of fibrosis.
H&E, reactive (chronic) lymphadenitis: follicular hyperplasia, an enlarged follicle with a pale germinal centre ringed by a dark mantle of small lymphocytes.
Image: “Follicular lymphatic hyperplasia, HE” by User:Patho, CC BY-SA 3.0, via Wikimedia Commons.
Examples: classic histological patterns of chronic lymphadenitis:
- Follicular hyperplasia: rheumatoid arthritis, early HIV, toxoplasmosis
- Caseating granulomas: tuberculosis
- Non-caseating granulomas: sarcoidosis
- Stellate necrotizing granulomas with neutrophils: cat-scratch disease (Bartonella henselae)