Approach to cancer in small animals
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List the different presentations of cancer
- Superficial lump/mass
- May be large and obvious
- May present as non-specific clinical signs as a direct effect of internal tumour e.g. vomiting, diarrhoea, weight loss/wasting
- May present with haematological abnormalities
- May present with neoplastic syndrome
What are the three steps when making a diagnosis?
- Take a thorough history
- Take a biopsy for histopathology
- Take a fine needle aspirate for cytology
Give examples of questions you would ask during your history
- Age/sex/breed of animal
- When was it first noticed?
- Rate of growth?
- Previous lumps or bumps?
What does a biopsy give us information about?
Tissue architecture and tumour grading
What are the advantages/disadvantages of biopsy?
- A - most accurate and definitive diagnosis
- D - expensive, time consuming, requires local/sedation or GA
What is tumour grading?
Assessment of the degree of malignancy as determined by a pathologist
What is the criteria for tumour grading?
- Cellular differentiation, pleomorphism
- Mitotic index
- Amount of necrosis
- Overall cellularity
- Stomal/inflammatory reaction
What are the tumour grades for a) sarcomas b) mast cell tumours?
- a) High grade - needs aggressive treatment and chemotherapy, low grade - local surgery usually sufficient, intermediate grade - local treatment +/- chemotherapy
- b) high grade - needs aggressive treatment and chemotherapy, low grade - local surgery usually sufficient
How much tissue should you biopsy?
As much as possible within reason
What type of tissue should you take for a biopsy?
Choose a representative area - avoid inflamed, necrotic, ulcerated tissue. Include a margin of the lesion and some normal tissue if possible.
What are the different types of biopsy?
- Incisional (wedge)
- Excisional (whole mass)
- Surface grab
- Needle core
What are the advantages/disadvantages of fine needle aspirate?
- A - quick, easy, cheap, no GA
- D - can be unrepresentative, does not provide information about tissue architecture
What are the steps involved in fine needle aspirate?
Suck out cells from mass, expel onto glass slide, smear the aspirate, stain and examine under microscope
What are some other methods for cell collection for cytology?
- Ultrasound guided aspirates
- Bone marrow aspirates
- Impression smears
- Cytospins of washes/lavages
What is tumour staging?
Defining the anatomical extent of the tumour in terms of primary site and distant spread determined by a clinician
At what concentration of cells is a tumour first palpable?
Why do we do tumour staging?
To decide whether treatment/what treatment is feasible
What system is used for tumour staging?
What does T stand for?
What do we asses in the primary tumour?
- Measure its dimensions with a ruler or callipers
- Assess whether there is local invasion
- Are there multiple primary lesions
- Use imaging to assess internal masses
What does N stand for?
Local lymph nodes
What do we asses in the local lymph nodes?
- Palpate them - are they hard? fixed? enlarged?
What does M stand for?
What are the four ways metastases can spread?
- Lymphatics (carcinomas, MCT)
- Haematogenous (sarcomas)
- Direct extension along tissue planes
- Seeding across thoracic/peritoneal cavity
What do we asses in the distant metastases?
- Physical examination
- Laboratory evaulation - organ function
- FNA/biopsy to confirm suspicions
What would you like to do?
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