Oncology: A clinical approach

Question 1

Approximately how many animals over the age of 10 have some type of cancer?

Answer 1

50%

Question 2

Name some dog breeds that are highly susceptible to cancer

Answer 2

Irish water spaniel 
Boxer
Flat coated retriever 
Rottweiller
Staffy 
Bernese mountain dog

Question 3

What are the three golden rules of clinical oncology?

Answer 3

1. Establish the diagnosis
2. Establish the extent/stage of the disease
3. Investigate any complications

Question 4

What are the pro’s and cons of an FNA?

Answer 4

enables us to distinguish between inflammatory and neoplastic lesions but you cannot grade from one

Question 5

To carry out histology, what types of biopsy can you take?

Answer 5

Needle biopsy, punch biopsy, incisional, excisonal biopsy

Question 6

How can we establish the extent of metastasis/size of the tumour?

Answer 6

Thoracic radiography - standard for tumours spread by haematogenous route
Ct is the modality of choice for bony lesions

Question 7

Where should you take biopsy from?

Answer 7

The probable surgical or radiotherapy field and not crossing any anatomical planes so as not to encourage metastasis

Question 8

When might we perform an incisional biopsy?

Answer 8

When a mass will not exfoliate well for a FNB or is too hard for a punch biopsy

Question 9

What should our incisional biopsy be like?

Answer 9

Narrow and cross sectional

Question 10

What type of tumours are best candidates for surgical removal?

Answer 10

Untreated tumours tend to have more normal surrounding anatomy, which facilitates surgical removal

Question 11

What considerations need to be made for surgical removal of previously treated tumours?

Answer 11

Recurrent tumours may have seeded to previously unaffected tissue planes = need wider, deeper resection
Patients with recurrence often have less normal tissue for closure

Question 12

Why must we use a large margin for tumour removal?

Answer 12

The edges contain the most active parts of tumours (best blood supply) so sub-total resection may leave behind most aggressive components

Question 13

What are Debulking/intralesional/cytoreductive excisions?

Answer 13

Leaves macroscopic volumes of tumour.

Will recur unless given adjuvant therapy (which is less effective if gross vs microscopic tumour remains)

Question 14

What is a marginal excision?

Answer 14

Excision immediately outside the pseudocapsule of the tumour, leaving behind microscopic volumes of tumour. Local recurrence likely without adjuvant therapy (Pseudocapsule of tumour = compressed tumour cells rather than connective tissue)

Question 15

What is a wide excision?

Answer 15

Removal of the tumour with complete margins of normal tissue in all directions.
Local recurrence unlikely.

The most effective natural barriers to the spread of cancer are collagen-rich relatively avascular tissues, including fascia, ligaments, tendons and cartilage
Fat, subcutaneous tissue, muscle and other parenchymatous organs offer relatively little resistance to invading tumour cells

Question 16

What is a Radical (or compartmental) excision?

Answer 16

Removal of an entire anatomical structure or compartment containing the tumour e.g. limb amputation for a primary bone tumour, or mastectomy.
Local recurrence unlikely.

Often applies for sarcomas (which can extend along fascial planes rather than through them)

Question 17

What considerations should be given to surgical scars from previous excisions?

Answer 17

Surgical scars will contain neoplastic cells, so should be given the same margins as the tumour