Neoplasia 6

Question 1

TUMOUR SUSCEPTIBILITY IN DOGS

Answer 1

LYMPHOMA/SARCOMA- Boxers
MALIGNANT HISTIOCYTOSIS- Bernese Mountain Dog
DISSEMINATED HISTIOCYTIC SARCOMA- Several breeds
HEMANGIOSARCOMA- GSD
OSTEOSARCOMA- Giant breeds, boxer, GSD, rottweiler
MAST CELL TUMOUR (SKIN)- Boxer, bulldog, retriever.

Question 2

DIAGNOSIS OF NEOPLASIA

Answer 2

Cytology

Biopsy

Question 3

CYTOLOGY

Answer 3

Where do we get cells from?
-Cells shed naturally in to body fluids- urine, CSF, fluid in pleural or peritoneal cavities.

• Cells obtained by exfoliation- tracheal wash, prostatic wash
• Cells aspirated by needle- blood, bone marrow, needle aspiration of solid tumours.

Question 4

BIOPSY

Answer 4

• NEEDLE- Core of tissue 1-2mm wide, 2cm long.
• ENDOSCOPIC- Small forceps collect smal (2-3mm) fragments. GI tract, respiratory tract, genitourinary tract.
• INCISION- Sample of lesion removed with a scalpel.
• EXCISION- Entire tumour removed.

Question 5

FEATURES OF MALIGNANCY

Answer 5

Look for these in a biopsy.

• Abnormal morphology
• Invasion/metastasis
• High mitotic index/abnormal mitoses
• High nucleus to cytoplasm (N:C) ratio
• Absence of encapsulation
• Lack of differentiation

Question 6

DIFFERENTIALS FOR CANINE ROUND CELL TUMOURS

Answer 6

• Lymphoma/sarcoma
• Canine cutaneous histiocytoma
• Mast cell tumour
• Plasmacytoma
• (Transmissible venereal tumour, TVT)

Question 7

LYMPHOMA/LYMPHOSARCOMA

Answer 7

Sheets of round cells with nucleus (open faced, nucleoli visible) and cytoplasm visible.

Lymphosarcomas can be typed using immunohistochemistry- CD3 detects T cells.
CD79a detects B cells.
Positive is brown.

Question 8

CLINICAL ONCOLOGY

Answer 8

Tumour grading- an assessment of degree of differentiation- high/medium/low. eg. Mast cell tumours, grade I, II, III.

• Mitotic rate
• Degree of necrosis
• Location
• Invasiveness

Question 9

MAST CELL TUMOURS

Answer 9

OLD grading method:
PATNAIK GRADE I- Well differentiated, good prognosis with complete excision.
PATNAIK GRADE II- Wide range of possible behaviours, from resolution with excision to widespread metastasis. Proloferation markers- Ki67.
PATNAIK GRADE III- Malignant, invasive, metastatic.

Prognosis- >1.8% positive on Astra blue stain gives a poor prognosis.

Question 10

MAST CELL TUMOURS- NEW GRADING METHOD

Answer 10

HIGH GRADE- If one of the following applies:

• Greater than 7 mitotic figures per 10 HPF high power field)
• Greater than 3 multinucleated cells per 10 HPF
• Greater than 3 bizarre nuclei per 10 HPF
• > 10% karyomegalic cells.

Question 11

TUMOUR STAGING

Answer 11

Uses the TNM method:
T- Primary tumour size/local invasion
N- ‘Nearby’ (regional) lymph node involvement
M- Extent of metastasis.

TNM Stage I- Single node involvement
Stage II- Multiple nodes in a regional area
Stage III- Generalised lymphadenopathy
Stage IV- Liver and/or spleen involvement
Stage V- Bone marrow, blood and/or non lymphoid organ involvement.

Substage a- Without clinical signs of disease.
Substage b- With clinical signs of disease.

Then, we can make a therapeutic plan and make a prognosis.

Question 12

ANIMAL MODELS OF CANCER- NATURALLY OCCURRING

Answer 12

• Avian leukosis
• Bovine lymphosarcoma
• Feline leukaemia
• > studies in viral induction

Canine models are becoming increasingly useful.
Genome characterised, rapid development of metastatic disease- particularly osteosarcoma, lymphosarcoma.

Question 13

ANIMAL MODELS OF CANCER- EXPERIMENTALLY INDUCED

Answer 13

Aim to produce rapid, reproducible induction in large population.
Mouse has a well defined genome, and genetically engineered mice are easily producable, with specific genes activated or suppressed.
-Transgene- an introduced gene.
-KO- lack of normal functioning gene.