Felis ISSN 2398-2950

Lymphadenopathy

Synonym(s): Lymphadenomegaly

Contributor(s): Ansar Ahmed, Michael Day, Gerry Polton

Introduction

  • Enlargement of lymph nodes is a common clinical finding in cats with a wide range of underlying disease states, but may sometimes be the primary presenting complaint. 
  • Technically, the term lymphadenomegaly is the correct description for lymph node enlargement, but lymphadenopathy (lymph node pathology) is generally used synonymously. 
  • Lymphadenopathy may involve peripheral (palpable) lymph nodes and/or internal visceral lymph nodes (as determined by imaging examination). 
  • Lymphadenopathy may be localized (solitary or regional) or generalized in distribution. The differential diagnosis of lymphadenopathy is important. Not all lymph node enlargement is attributed to neoplastic change, and there are numerous causes of relatively benign lymphadenopathy. Finally, there are some exceptions to these general comments:
  • 'Lymphadenopathy' might also encompass situations where lymph nodes are reduced in size, for example in senility, cachexia or with viral infection or immunosuppression that depletes lymphoid tissue.  Further, lymph nodes might display pathological change (eg the presence of metastatic tumor) without necessarily being enlarged.
Follow the diagnostic tree for Peripheral lymphadenopathy Peripheral lymphadenopathy.

Pathogenesis

Pathophysiology

  • Lymphadenopathy is not generally considered a specific disease entity, but is an important clinical finding, the cause for which should be ascertained whenever it is recognized. There are numerous differential diagnoses for canine lymphadenopathy. The investigation of lymphadenopathy is generally one part of an overall clinical examination, and the interpretation of lymphadenopathy should always be made in light of all that is known about other local or systemic disease in the patient. 
  • The first distinction that is made in the investigation of lymphadenopathy is whether the change is localized or generalized. Enlargement of a single lymph node, or unilateral enlargement of paired lymph nodes, most likely reflects pathological change in the tissue drained by that node, eg oral infectious or neoplastic disease will often result in uni- or bilateral submandibular lymphadenopathy.  Enlargement of multiple lymph nodes, particularly at distant sites not directly related to each other, is a potentially more significant clinical finding and suggests a multisystemic or multifocal disease process.
  • The single most common cause of lymphadenopathy in the cat is primary lymphoid neoplasia (lymphoma) affecting the node. In contrast to the situation in dogs, generalized lymph node enlargement is a very rare manifestation of lymphoma in cats and should trigger consideration of an infectious or autoimmune disease process.
  • The pathogenesis of lymphoma Lymphoma is discussed elsewhere. 
  • Reactive hyperplasia is the most common cause of benign lymphadenopathy, and simply reflects activity of the node as part of a local or general immune response. Hyperplasia (increased cell number) involves the cortical (follicular) and paracortical B and T lymphocytes respectively, and the plasma cells of the medullary cords. Reactive lymph nodes have increased lymphatic flow and there is evidence of this increased drainage from tissue from the presence of numerous phagocytic cells (macrophages and dendritic cells) within the medullary sinuses (sinus histiocytosis).
  • Lymphadenitis is inflammation of the lymph node. Most commonly, this is a sequel to an inflammatory/infectious process in the tissue drained by the node with the node becoming secondarily involved in the same process.  Some such processes will however have a primary focus within the node in the absence of local tissue changes.  There is a wide range of infectious causes of lymph node enlargement, but in general pathogens that induce chronic inflammation (particularly intracellular pathogens) are most likely to induce this type of lymph node pathology. Mycobacterial infection and feline infectious peritonitis Feline infectious peritonitis are good examples of this type of pathology. Increasingly, pathologists recognize a syndrome of 'sterile granulomatous lymphadenopathy' where there is inflammatory change in an enlarged lymph node, but conventional methodology fails to demonstrate an infectious cause. This syndrome most likely represents infection with an unconventional pathogen that might require more sensitive molecular diagnostic approaches.
  • Lymph node enlargement secondary to metastatic spread of neoplasia can involve any lymph node draining malignant neoplastic tissue. Lymph node enlargement due to a range of other causes (hemorrhage, infarction, edema) might occur - but again often reflects changes in local or surrounding tissues.
  • Methimazole Methimazole administration for hyperthyroidism has been associated with an atypical lymphoid hyperplasia characterized by B and T cell proliferation. Resolution follows withdrawal of the inciting cause.

Diagnosis

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Treatment

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Further Reading

Publications

Refereed papers

  • Recent references from PubMed and VetMedResource.
  • Addie D, Belák S, Boucraut-Baralon C et al (2009) Feline infectious peritonitis. ABCD guidelines on prevention and management. J Feline Med Surg 11 (7), 594-604 PubMed.
  • Niessen S J, Voyce M J, de Villiers L et al (2007) Generalised lymphadenopathy associated with methimazole treatment in a hyperthyroid cat. J Small Anim Pract 48 (3), 165-168 PubMed.
  • Brömel C, Sykes J E (2005) Histoplasmosis in dogs and cats. Clin Tech Small Anim Pract 20 (4), 227-232 PubMed.
  • Ruiz de Gopegui R, Peñalba B & Espada Y (2004) Causes of lymphadenopathy in the dog and cat. Vet Rec 155 (1), 23-24 PubMed.
  • Fan T M (2003) Lymphoma updates. Vet Clin North Am Small Anim Pract 33 (3), 455-471 PubMed.
  • Rogers K S, Barton C L & Landis M (1993) Canine and feline lymph nodes.  Part I.  Anatomy and function. Comp Contin Educ Pract Vet 15 (3), 397-408 VetMedResource.
  • Rogers K S, Barton C L & Landis M (1993) Canine and feline lymph nodes. Part II.  Diagnostic evaluation of lymphadenopathy. Comp Contin Educ Pract Vet 15 (11), 1493-1503 VetMedResource.

Other sources of information

  • Day M J (1999) Diseases of lymphoid tissue. In: M J Day. Clinical Immunology of the Dog and Cat. Manson Publishing, London. pp. 250-265.


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