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Lymph Node Normal Morphology. Cortex Primary Follicle Secondary Follicle Mantle Zone Paracortex Medulla Sinuses. Cortex. Primary B-Cell Follicles Nodules of small lymphocytes Lack germinal centers Secondary B-Cell Follicles Result of stimulation Germinal Centers Mantle zone.

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lymph node normal morphology
Lymph Node Normal Morphology
  • Cortex
    • Primary Follicle
    • Secondary Follicle
    • Mantle Zone
  • Paracortex
  • Medulla
    • Sinuses
cortex
Cortex
  • Primary B-Cell Follicles
    • Nodules of small lymphocytes
    • Lack germinal centers
  • Secondary B-Cell Follicles
    • Result of stimulation
    • Germinal Centers
    • Mantle zone
germinal centers
Germinal Centers
  • Pale zone
    • toward antigen entry
    • small cleaved cells / centrocytes
    • follicular dendritic cells
  • Dark zone
    • toward paracortex
    • large lymphoid cells / centroblasts
    • tingible body macrophages
mantle zone
Mantle Zone
  • polarized toward antigen entry
  • express bcl-2 protein
paracortex
Paracortex
  • rich in T cells
  • CD4:CD8 ratio variable
  • interdigitating dendritic cell
    • S-100 positive
    • irregular vesicular nuclei
  • high endothelial venules
    • postcapillary vessel
    • cuboidal epithelium
medullary areas
Medullary areas
  • B cells predominate especially plasma cells
  • histiocytes
handling the fresh specimen
Handling the Fresh Specimen
  • Surgeon should excise the largest and most abnormal node
  • Tissue for histology
  • Touch imprints
  • Fresh / frozen tissue for immunologic studies
  • Sterile portion for cytogenetics
frozen section
Frozen Section
  • Diagnostic frozen section should be discouraged
  • Use frozen to assess adequacy or triage tissue
freezing for immunologic studies
Freezing for Immunologic Studies
  • Liquid nitrogen or isopentane / dry ice mix is best
  • Thin sections (<2 mm )may be frozen in OCT
  • OCT must be wrapped in foil / plastic to avoid desiccation
  • Store at -70°C ideal but -20°C suitable for many antigens
fixation
Fixation
  • Node sliced in 2-3 mm intervals
  • One metal based fixative (B5, Zenkers, zinc sulfate)
  • One neutral buffered formaldehyde (formalin)
processing
Processing
  • Single most important factor for optimal histology is section thickness
  • Sections should be one cell layer thick
routine stains
Routine Stains
  • H&E
  • Giemsa - highlight nuclear features, cytoplasmic granules and plasmacytoid features
  • PAS - highlights mucin and glycogen, immunoglobulin inclusions and blood vessels
  • Methyl-green pyronin - highlights plasmacytoid features
common errors in fixation and processing
Common Errors in Fixation and Processing
  • Drying of specimen - dark edge artifact; autolysis if prolonged
  • Section >3 mm thick - soft unfixed core; center cells show ballooning and are pale
  • Overfixation in B5 - brittle tissue; decreased nuclear staining
  • Inadequate dehydration - numerous cracks (dry earth look)
common errors in fixation and processing14
Common Errors in Fixation and Processing
  • Paraffin too hot - muddy staining with poor detail
  • Improper sectioning - Venetian-blind effect; poor cytologic detail
  • Section drying too hot - bubbled nuclei and antigen loss