Lymph Nodes
Normal architecture
Response to stimulation
Non-neoplastic changes
Normal Architecture
The lymph node consists of an inner medullary area rich in plasma cells
and an outer cortical region. The node is surrounded by a sinus and
then a capsule. Afferent lymphatics drain into this sinus, bringing
new antigens to the node for presentation. An unstimulated node's
cortex contains primary follicles composed of B cells (CD 19, 20, 22) and
some dendritic cells (CD 21, 23, 35) surrounded by paracortical T cells.
Reponse to Stimulation
When antigens are delivered to lymph nodes, secondary follicles develop.
Secondary follicles are larger than primary follicles. The cells
composing the primary follicle are displaced to the edges of the follicle
and form a mantle. These follicles are larger in size than the primary
follicles and exhibit polarization. The side of the follicle closest
to the hilum has larger, darker cells than the more distal portions.
These cells are centroblasts, and the lighter cells with irregular and
cleaved nuclei are centrocytes. Centroblasts have a high mitotic
rate and their nuclei are not cleaved. Macrophages with tingible
material may also be present. Outside the mantle zone, nearer to
the sinus is a group of B cells known as the marginal zone.
Non-neoplastic changes
Acute non-specific lymphadenitis
Nodes develop necrotic centers, large germinal centers.
The sinus lining may become cuboidal.
Chronic lymphadenitis
Secondary follicles develop in response to chronic infection,
such as HIV, toxoplasmosis and rheumatoid arthritis.
Paracortical Lymphoid Hyperplasia
Large T cells, immunoblasts, are present in the paracortical
region.
Sinus Histiocytosis
Histiocytes often accumulate in the sinuses as a result of
drainage from remote cancer.
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Last modification: April 30, 1999