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Lymphoma and plasma cell neoplasms

Lymph nodes

Normal histology


Reviewer: Nikhil Sangle, M.D., University of Utah and ARUP Laboratories (see Reviewers page)
Revised: 22 October 2012, last major update January 2011s
Copyright: (c) 2001-2012, PathologyOutlines.com, Inc.

Structures
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● Germinal center: round/oval zone containing pale staining cells, surrounded by darker cells
● Mantle zone: small unchallenged B cells surrounding pale staining germinal centers
● Marginal zone: light zone surrounding follicles; contains post-follicular memory B cells derived after stimulation of recirculating cells from T cell dependent antigen; named ‘marginal cells’ due to location at interface of lymphoid white-pulp and non-lymphoid red pulp in the spleen; however, marginal zone is rarely seen except in mesenteric nodes (APMIS 2002;110:325)
● Sinuses: direct the flow of lymph from the afferent lymphatics, to the subcapsular sinus, to the trabecular sinus, to the medullary sinus, to the efferent lymphatics (see diagram below)
● Reference: Toxicol Pathol 2006;34:409

Cell types
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● Centroblasts: large non-cleaved follicular center cells with moderate amounts of basophilic cytoplasm, round nuclei, open chromatin, multiple peripheral nucleoli
● Centrocytes: small cleaved follicular center cells with scant cytoplasm

Diagrams
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Lymph node architecture

Micro images
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Primary and secondary follicles in cortex adjacent to paracortical T zone. The subcapsular sinus connects to the medullary sinuses via trabecular sinuses (right) (AFIP 3rd Series Vol 14)


The nodule of small lymphocytes at top merges with the paracortical T zone at bottom (AFIP 3rd Series Vol 14)

   
Centroblasts (left) and centrocytes (right)


B cells (CD20+, blue) predominate in the primary and secondary follicules and medullary cords, but T cells (CD43+, red) predominate in the paracortex (AFIP 3rd Series Vol 14)


In this tonsil specimen, the mantle zole and the pale zone of the germinal center are polarized towards the top, reflecting the site of antigen entry at the epithelial surface (AFIP 3rd Series Vol 14)


Ki-67 nuclear staining highlights proliferating cells in the dark zone of the germinal center (bottom), away from the site of antigen entry at the top (see above image also) (AFIP 3rd Series Vol 14)


Ki-67 nuclear staining of the germinal center and paracortex of tonsil (AFIP 3rd Series Vol 14)


CD35 stains follicular dendritic cells in the germinal center (although CD21 and CD23 are more commonly used) (AFIP 3rd Series Vol 14)


The germinal center does NOT stain with bcl2, but mantle zone cells and T cells are bcl2+ (AFIP 3rd Series Vol 14)


The germinal center of this secondary follicle has an unusually large number of cells with cytoplasmic immunoglobulin (kappa-red, lambda-blue). The kappa/lambda ratio is 2-3:1, which is normal (AFIP 3rd Series Vol 14)

   
Mantle cell lymphocytes are kappa+ (left) and lambda+ (right). Most staining in the germinal center is confined to follicular dendritic cell processes, in the form of immune complexes. Scattered plamsa cells with strong staining are also seen near the surface of this tonsil specimen (AFIP 3rd Series Vol 14)


Small lymphocytes surround the high endothelial venules, a marker for the paracortical T zone (AFIP 3rd Series Vol 14)


CD4+ T cells (blue) and CD8+ T cells (red) surround the high endothelial venule in the center (AFIP 3rd Series Vol 14)


There are both naive T cells (CD45RA, blue) and memory T cells (CD45RO, red) in this mesenteric lymph node (AFIP 3rd Series Vol 14)


Interdigitating dendritic cells (S100+, brown) are adjacent to T cells (CD43+, blue) (AFIP 3rd Series Vol 14)

Positive stains
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● Germinal centers have strong dense bcl6 and CD10 expression
● TdT (terminal deoxynucleotidyl transferase) is expressed by premature B and T cells
● B cells express CD19, CD20, CD79a
● Antigen stimulated B cells with the capacity to differentiate toward plasma cells express MUM1/IRF4 and CD138
● T cells express CD2, CD3, variable CD4 and CD8

End of Lymphoma and plasma cell neoplasms > Lymph nodes > Normal histology of lymph nodes


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