Histopathology of Tumours

Grading Neoplasia

  • Most important
    • Mitotic Figures
    • Necrosis
  • Next
    • Anaplasia
    • Pleomorphism
    • Atypia

Techniques

Standard Microscopy

  • Specimen fixed in Formalin
    • Decalcified if contains bone/ calcium
  • Embedded in Paraffin
    • Water replaced with wax
  • Fine sections cut
  • Stained with Haematoxylin & Eosin
    • Haematoxylin stains Protein blue
    • Eosin stains Cytoplasm & Collagen pink

Special Stains

  • Van Gieson’s
    • Myogenic Tumours
  • Reticulin
    • Vascular tumours
    • Clear cell Sarcoma
    • Alveolar Soft Part Sarcoma
  • Periodic Acid Shift
    • Ewing’s/ PNET
    • Rhabdomyosarcoma
    • Neuroblastoma
  • Melanin
    • Melanoma
  • Masson’s Trichrome Stain
    • Fibrosarcoma (detects presence of collagen)

Frozen Section

  • Specimen fresh
  • Specimen frozen with liquid N²
  • Fine sections cut
  • Similarly stained

Electron Microscopy

  • Rationale
    • Certain ultrastructural features differentiate tumour types
  • Differentiate PNET/ Ewing’s / Neuroblastoma
  • Epithelial structures in carcinoma
  • Sarcomeres in Myosarcoma
  • Melanosomes in Melanoma

Immunohistochemical Stains

  • Rationale
    • Identifies certain proteins
  • Technique
    • Slide prepared as above
    • Particular Antibody-containing solutions put on slide
      • Antibody binds with antigen if particular protein present
      • Then another antibody with attached colouring agent put on slide
      • Binds to antigen-antibody complex if present
    • Thus stains if protein of interest present
  • Types IHC Stains
S100Melanoma
Schwann/ Neural cells
Ewing’s / PNET
Actin Muscle,
Myofibroblasts
DesminMuscle
MyoglobinSkeletal muscle only
VimentinEverything
LCALymphoma
CytokeratinSkin
Synovial Sarcoma
Epithelioid Sarcoma
Epithelial Membrane AntigenSynovial Sarcoma
Epitheliod Sarcoma
NSE, GFAP, Neurofilament PRRound Cell Tumours
Types IHC Stains

DNA Ploidy

  • Measure DNA content in each cell by flow cytometry
  • Quantify number of cells with normal & abnormal amounts DNA
  • Normal 23 pairs (Diploid) or 46 total
  • Little benefit as
    • Can’t use it to grade neoplasia
    • Can’t use it for prognosis
    • Can’t diagnose tumour type

Cytogenetics

  • Rationale
    • Certain tumours have identified genetic abnormalities
      • Ewing’s/ PNET t(11,22)
      • Synovial Sarcoma t(X, 18)
      • Liposarcoma
      • Rhabdomyosarcoma
      • Infantile Fibrosarcoma Trisomy 11,17,20
      • Clear Cell Sarcoma t(11, 22)
  • Technique
    • Cells cultured
    • Halted in Metaphase
    • Karyotyping performed
    • Chromosomal banding patterns identified