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==Pathophysiology==
==Pathophysiology==
* If an [[infection]] remains untreated, the center of the node may become necrotic, resulting in the accumulation of fluid and debris within the structure. This is known as an abscess and feels a bit like a tensely filled balloon or grape (a.k.a. fluctuance). Knowledge of which nodes drain specific areas will help search efficiently. Following infection, lymph nodes occasionally remain permanently enlarged, though they should be non-tender, small (less the 1 cm), have a rubbery consistency. It is common, for example, to find small, palpable nodes in the submandibular/ tonsilar region of otherwise healthy individuals. This likely represents sequelae of past pharyngitis or dental infections.
==Pathophysiology==
* [[Malignancies]] may also involve the lymph nodes, either primarily (e.g. [[lymphoma]]) or as a site of metastasis. In either case, these nodes are generally firm, non-tender, matted (i.e. stuck to each other), fixed (i.e. not freely mobile but rather stuck down to underlying tissue), and increase in size over time. The location of the lymph node may help to determine the site of malignancy. Diffuse, bilateral involvement suggests a systemic malignancy (e.g. lymphoma) while those limited to a specific anatomic region are more likely associated with a local problem. Enlargement of nodes located only on the right side of the neck in the anterior cervical chain, for example, would be consistent with a [[squamous cell carcinoma]], frequently associated with an intra- oral primary cancer.
Lymph nodes are part of the immune system. As such, they are most readily palpable when fighting infections. Infections can either originate from the organs that they drain or primarily within the lymph node itself, referred to as [[lymphadenitis]].*The pathogenesis of lymphadenopathy is characterized by the inflammation of lymph nodes. This process is primarily due to an elevated rate of trafficking of lymphocytes into the node from the blood, exceeding the rate of outflow from the node.<ref name="pmid24753638">{{cite journal |vauthors=Mohseni S, Shojaiefard A, Khorgami Z, Alinejad S, Ghorbani A, Ghafouri A |title=Peripheral lymphadenopathy: approach and diagnostic tools |journal=Iran J Med Sci |volume=39 |issue=2 Suppl |pages=158–70 |year=2014 |pmid=24753638 |pmc=3993046 |doi= |url=}}</ref>
* Diffuse upper airway infections (e.g. [[mononucleosis]]), systemic infections (e.g. [[tuberculosis]]) and inflammatory processes (e.g. [[sarcoidosis]]) can also cause lymphadenopathy (i.e. lymph node enlargement). This can be either symmetric or asymmetric.
*The immune response between the antigen and lymphocyte that leads to cellular proliferation and enlargement of the lymph nodes.  
===Microscopic Pathology===
*Lymph nodes may also be enlarged secondarily as a result of the activation and proliferation of antigen-specific T and B cells (clonal expansion).  
===Patterns of Benign (Reactive) Lymphadenopathy===
*On gross pathology, characteristic findings of lymphadenopathy, include:
There are three distinct patterns of benign lymphadenopathy:
:*Enlarged [[lymph node]]
*Follicular hyperplasia: Seen in infections, autoimmune disorders, and nonspecific reactions.
:*Soft greasy yellow areas within the capsule
*Paracortical hyperplasia: Seen in viral infections, skin diseases, and nonspecific reactions.
 
*Sinus histiocytosis: Seen in lymph nodes draining limbs, inflammatory lesions, and malignancies.
==Microscopic findings==
*On microscopic histopathological analysis, characteristic findings of lymphadenopathy will depend on the etiology.Common findings, include:<ref name="pmid24753638">{{cite journal |vauthors=Mohseni S, Shojaiefard A, Khorgami Z, Alinejad S, Ghorbani A, Ghafouri A |title=Peripheral lymphadenopathy: approach and diagnostic tools |journal=Iran J Med Sci |volume=39 |issue=2 Suppl |pages=158–70 |year=2014 |pmid=24753638 |pmc=3993046 |doi= |url=}}</ref>
 
'''Non-specific reactive follicular [[hyperplasia]] (NSRFH)'''
:*Large spaced cortical follicles
:*Tingible body [[macrophages]], normal dark/light GC pattern
'''Lymph node metastasis'''
:*Foreign cell population (usually in subcapsular sinuses)
:*+/-nuclear [[atypia]]
:* +/-malignant architecture
'''Toxoplasmosis'''
:*Large [[follicles]]
:*Epithelioid cells perifollicular & intrafollicular
:*Reactive GCs
:*Monocytoid cell clusters
'''Cat-scratch disease'''
:*PMNs in necrotic area
:*"Stellate" (or serpentine) shaped micro-abscesses
:*Presence of granulomas
'''Dermatopathic lymphadenopathy'''
:*Melanin-laden histiocytes
:*Histiocytosis
'''Systemic lupus erythematosus lymphadenopathy'''
:*Blue hematoxylin bodies
:*[[Necrosis]]
:*No PMNs


==References==
==References==

Revision as of 19:01, 30 January 2019

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Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]; Associate Editor(s)-in-Chief: Raviteja Guddeti, M.B.B.S. [2]

Overview

Lymph nodes are part of the immune system. As such, they are most readily palpable when fighting infections. Infections can either originate from the organs that they drain or primarily within the lymph node itself, referred to as lymphadenitis.

Pathophysiology

Pathophysiology

Lymph nodes are part of the immune system. As such, they are most readily palpable when fighting infections. Infections can either originate from the organs that they drain or primarily within the lymph node itself, referred to as lymphadenitis.*The pathogenesis of lymphadenopathy is characterized by the inflammation of lymph nodes. This process is primarily due to an elevated rate of trafficking of lymphocytes into the node from the blood, exceeding the rate of outflow from the node.[1]

  • The immune response between the antigen and lymphocyte that leads to cellular proliferation and enlargement of the lymph nodes.
  • Lymph nodes may also be enlarged secondarily as a result of the activation and proliferation of antigen-specific T and B cells (clonal expansion).
  • On gross pathology, characteristic findings of lymphadenopathy, include:
  • Enlarged lymph node
  • Soft greasy yellow areas within the capsule

Microscopic findings

  • On microscopic histopathological analysis, characteristic findings of lymphadenopathy will depend on the etiology.Common findings, include:[1]

Non-specific reactive follicular hyperplasia (NSRFH)

  • Large spaced cortical follicles
  • Tingible body macrophages, normal dark/light GC pattern

Lymph node metastasis

  • Foreign cell population (usually in subcapsular sinuses)
  • +/-nuclear atypia
  • +/-malignant architecture

Toxoplasmosis

  • Large follicles
  • Epithelioid cells perifollicular & intrafollicular
  • Reactive GCs
  • Monocytoid cell clusters

Cat-scratch disease

  • PMNs in necrotic area
  • "Stellate" (or serpentine) shaped micro-abscesses
  • Presence of granulomas

Dermatopathic lymphadenopathy

  • Melanin-laden histiocytes
  • Histiocytosis

Systemic lupus erythematosus lymphadenopathy

  • Blue hematoxylin bodies
  • Necrosis
  • No PMNs

References

  1. ↑ 1.0 1.1 Mohseni S, Shojaiefard A, Khorgami Z, Alinejad S, Ghorbani A, Ghafouri A (2014). "Peripheral lymphadenopathy: approach and diagnostic tools". Iran J Med Sci. 39 (2 Suppl): 158–70. PMC 3993046. PMID 24753638.

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