Lymphadenopathy pathophysiology
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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
- 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.
- 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.
- 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.
Microscopic Pathology
Patterns of Benign (Reactive) Lymphadenopathy
There are three distinct patterns of benign lymphadenopathy:
- Follicular hyperplasia: Seen in infections, autoimmune disorders, and nonspecific reactions.
- Paracortical hyperplasia: Seen in viral infections, skin diseases, and nonspecific reactions.
- Sinus histiocytosis: Seen in lymph nodes draining limbs, inflammatory lesions, and malignancies.