Lymph Node Normal Morphology

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Lymph Node Normal Morphology

• Cortex
• Primary Follicle
• Secondary Follicle
• Mantle Zone
• Paracortex
• Medulla
• Sinuses

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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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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

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Mantle Zone

• polarized toward antigen entry
• express bcl-2 protein

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Paracortex

• rich in T cells
• CD4CD8 ratio variable
• interdigitating dendritic cell
• S-100 positive
• irregular vesicular nuclei
• high endothelial venules
• postcapillary vessel
• cuboidal epithelium

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Medullary areas

• B cells predominate especially plasma cells
• histiocytes

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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

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Frozen Section

• Diagnostic frozen section should be discouraged
• Use frozen to assess adequacy or triage tissue

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Freezing for Immunologic Studies

• Liquid nitrogen or isopentane / dry ice mix is
  best
• Thin sections (lt2 mm )may be frozen in OCT
• OCT must be wrapped in foil / plastic to avoid
  desiccation
• Store at -70C ideal but -20C suitable for many
  antigens

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Fixation

• Node sliced in 2-3 mm intervals
• One metal based fixative (B5, Zenkers, zinc
  sulfate)
• One neutral buffered formaldehyde (formalin)

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Processing

• Single most important factor for optimal
  histology is section thickness
• Sections should be one cell layer thick

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Routine Stains

• HE
• 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

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Common Errors in Fixation and Processing

• Drying of specimen - dark edge artifact
  autolysis if prolonged
• Section gt3 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)

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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

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Antibodies Employed in Paraffin Tissue Sections
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Antibodies Employed in Paraffin Tissue Sections
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Antibodies Employed in Paraffin Tissue Sections
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Antibodies Employed in Paraffin Tissue Sections
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Antibodies Employed in Paraffin Tissue Sections
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Antibodies Employed in Paraffin Tissue Sections
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Antibodies Employed in Paraffin Tissue Sections
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Antibodies Employed in Paraffin Tissue Sections
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Antibodies Employed in Fresh or Frozen Tissue
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Antibodies Employed in Fresh or Frozen Tissue
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Antibodies Employed in Fresh or Frozen Tissue
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Antibodies Employed in Fresh or Frozen Tissue
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Antibodies Employed in Fresh or Frozen Tissue
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Antibodies Employed in Fresh or Frozen Tissue
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Antibodies Employed in Fresh or Frozen Tissue
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Antibodies Employed in Fresh or Frozen Tissue
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Antibodies Employed in Fresh or Frozen Tissue