Histopathology

Grading Neoplasia

 

Most important

 

Mitotic Figures

Necrosis

 

Next Important

 

Anaplasia

Pleomorphism

Atypia

  

Standard Microscopy

- specimen fixed in formalin

- decalcified if contains bone

- 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

- Rhabdomyosarc 

- Neuroblastoma

 

Melanin

- melanoma

 

Masson's Trichrome Stain

- presence of collagen = fibrosarcoma

 

Frozen Section

 

Specimen fresh

- specimen frozen with liquid nitrogen

- fine sections cut

- similarly stained

 

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

 

Keratin + / Vimentin -

- carcinoma

 

Keratin - / vimentin +

- sarcoma

 

Keratin + / Vimentin +

- synovial / epitheloid sarcoma

- adamantinoma

- osteofibrous dysplasia

- chordoma

 

S100 

- Melanoma

- Schwann / Neural cells

- Ewings / PNET

 

Factor VIII

- vascular tumour

 

MIC2

- Ewing's, PNET

 

Actin

- muscle, myofibroblasts

 

Desmin

- muscle

 

Myoglobin

- skeletal muscle only

 

LCA (leucocyte common antigen)

- lymphoma

- haemopoietic lesions

 

Cytokeratin

- skin

- synovial sarcoma

- epithelioid sarcoma

 

Epithelial Membrane Antigen

- synovial sarcoma

- epithelioid sarcoma

 

NSE, GFAP, Neurofilament PR 

- round cell tumours

 

DNA Ploidy

 

Measure DNA content in each cell by flow cytometry

- quantify no cell with normal & abnormal amounts DNA

- N = 23 pairs (Diploid) or 46 total 

 

Little benefit as

1. Not used to grade neoplasia

2. Not useful for prognosis

3. Can't diagnose tumour type

 

Cytogenetics

 

Rationale

- certain tumours have identified genetic abnormalities

 

Technique

- cells cultured

- halted in metaphase

- karyotyping performed

- chromosomal banding patterns identified

 

Examples

 

Ewings / PNET

- t (11, 22)

- EWS - FLI

 

Clear Cell Sarcoma t (12, 22)

 

Synovial Sarcoma t(X, 18)

 

Liposarcoma

Rhabdomyosarcoma

Infantile Fibrosarcoma

Trisomy 11, 17, 20

 

Electron Microscopy

 

Rationale

 

Certain ultrastructural features differentiate tumour types

 

DDx PNET/ Ewing's / Neuroblastoma

 

Epithelial structures in carcinoma

 

Sarcomeres in Myosarcoma

 

Melanosomes in Melanoma