General Veterinary Oncology

What is the leading cause of death in companion animals older than 2 years?

Cancer

T/F you will see pets with cancer?

True

What is cancer?

Out of control cellular growth

Why does cancer occur?

A series of mutations leads to cell cycle dysregulation

A multifactorial from causes such as diet, sun exposure, chemical exposure

What are proto-oncogenes?

Genes in normal cells that regulate growth and differentiation

What are some exmamples of proto-oncogenes?

Tyrosine kinases, transcription factors, HER2neu, myc

What happens when a proto-oncogene mutates?

It becomes a oncogene (cancerous)

What is a tumor suppressor gene?

Induce apoptosis in damaged cells to prevent growth and replication

What are some examples of tumor suppressor genes?

p53, Rb, BRCA

When are we able to diagnose cancer?

10^9 cancer cells 

What cancer is heritable in dogs?

Only renal cystadenocarcinoma and nodular dermatofibrosis of german shepherds

What breeds are more susceptible to cancer?

Boxers and goldens (50% chance)

What cancer is heritable in humans?

Many, one example is retinoblastoma

What are some causes of carcinogens?

Carcinogens

Viruses

Chemicals

Physical factors

Hormones

In humans, how many known carcinogens are there?

63

In humans, how many anticipated carcinogens are there?

193

What cancers do papillomaviruses cause?

Mucocutaneous in dogs

Dermal in cats

Sarcoids in horses

What retroviruses can cause cancer?

FeLV (20% chance PI animals will have cancer)

FIV (6x more likely for cancer)

What chemicals can cause cancer?

Environmental tobacco smoke (lymphoma in cats)

Pesticides, herbicides, insecticides (2,4-D, glyphosphate (roundup))

What does 2,4-D, glyphosphate (roundup) case?

Lymphoma or TCC

T/F flea and tick preventative can cause cancer?

False

What type of trauma/chronic inflammation can cause cancer?

Eye lesions

Metallic implants

Injection site sarcomas

Eye lesions can cause what cancers?

Corneal tumors in dogs

Intraocular sarcoma in cats

Why can injection sites cause sarcomas in cats?

Chronic inflammation. Seen with vaccines and long-acting/repeated injections

What type of cancer can UV radiation/sunlight cause?

SCC, cutaneous HSA

What are more susceptible to UV radiation/sunlight cancer?

Light pigmented animals

Sparse hair cover

What cancer does ionizing radiation cause?

Secondary tumors at sites of prior radiation treatment for a previous tumor

Usually sarcomas

How do tumor cells grow?

Log growth, very rapid initially

When are we able to diagnose tumors?

Not until there are already about 10^9 or 1 billion cells

When do tumors become deadly?

10^12 or about 1 kg of tumor mass

What is the range of tumor cells that you have to detect and save a patient?

10^9 - 10^12 (relatively small window)

When does chemo work best?

Cells that are rapidly dividing but we cannot detect until the tumor begins to slow down cell growth

Why is surgery so helpful when treating cancer?

By removing most of the tumor, it begins a rapid growth phase again where chemotherapy will be most effective

Why is it difficult to determine carcinogens in pets?

We do not often have a complete history of their entire life

What tumors do estrogen and progesterone cause?

mammary tumors

How do you reduce the risk for mammary tumors?

Early spay

What tumor does androgens/testosterone cause?

Perianal adenoma

What is the signalment for a perianal adenoma?

Intact males but can also occur in females

What do you do when presented with a mass?

Diagnosis

Staging

Treatment

How can you diagnose a mass?

Cytology

Histopathology

What are the benefits of cytology?

Cheap, quick, easy with fast results (need histopath to confirm)

What can a cytology be performed on?

FNA, impression smear, fluid

What are the 4 main cancer cell types?

Epithelial

Round cell

Mesenchymal

Endocrine

What do cancer cell has round nuclei, high N:C?

Round cell

What cancer cell is spindle to ovoid, with a lower N:C?

Mesenchymal

What cancer cell is polygonal, round nuclei, and clumps?

Epithelial

What cancer cell type is polygonal, round naked nuclei in a sea of cytoplasm?

Endocrine

Where are round cell tumors located?

WBC, mast cells, plasma cells

Where are mesenchymal cell tumors located?

Connective tissue like bone, muscle, fat

Where are epithelial cell tumors located?

Glands and body lining like liver, kidney, prostate etc

Where are endocrine cell tumors located?

Glands like anal gland thyroid or pancreas

Where do round cell tumors metastasis?

Lymphatics, spleen, liver

Where do mesenchymal cell tumors metastasis?

blood (lungs and organs)

Where do epithelial cell tumors and endocrine cell tumors metastasis?

Lymphatics then blood 

What cancer cell types exfoliate well?

Round cell (very well)

Epithelial

Endocrine

What cancer cell type does not exfoliate well?

Mesenchymal

What is the gold standard for diagnosis and the only way to get a grade?

Histopathology

What are the problems with histopathology?

More money, time, and skill

Takes longer

Only performed on tissue biopsy

How can you stage?

Blood work and urinalysis

Thoracic rads

Abdominal US

Bone marrow

Lymph node aspiration

How do you decide what tools to use for staging?

Based on tumor type and cell and where they tend to travel to

How can you treat tumors?

Cut

Poison (chemo)

Burn

What should you do every time you cut out a tumor?

Biopsy it (if its worth taking off, its worth knowing what it is)

What tumors burn off well?

Nasal and brain

What is important during the treatment phase?

Need to tell owner expectations

Discuss treatment options

Discuss costs

Referral is never wrong