Lecture Notes: Neoplasia and Tumors in Veterinary Medicine

Feline Leukemia Vaccination Concerns

The risk of fibrosarcoma from the feline leukemia vaccine is small, but present.
Decision to vaccinate should weigh the risk of fibrosarcoma against the risk of feline leukemia.
Fibrosarcoma is considered a significant concern due to its aggressive nature.

Neoplasia: Abnormal, uncontrolled cell growth that can spread aggressively.
- Neoplastic cells invade normal cells and take over.
Tumor: A mass with a neoplastic tendency; can be benign or malignant.
- The term tumor does not automatically imply abnormal cells.
Adenoma: Usually a benign tumor.

The distinction depends on:
- Growth Rate: How quickly the mass is expanding.
- Invasion: Whether it's invading surrounding tissues.
- Metastasis: Spreading to other body parts.
- Histopathologic Appearance: Microscopic evaluation of the cells.
Cancer: Interchangeable with malignant neoplasia.

Benign tumors can still be dangerous based on location and size.
Example of a lipoma in a dog that started small but grew into a large, weeping mass over several years.
- Easy to remove initially but became malignant due to neglect.
- Was not attached to deep subcutaneous layers, limiting its ability to spread to the lungs.
Metastasis to the lungs indicates a poor prognosis.

Case example: A client insisted on aggressive treatment for a cat with lung metastasis, even when the animal's quality of life was severely compromised.
Raised the question of whether treatment constituted animal abuse.
Highlights the importance of veterinarians advising against treatments with poor prognoses.

Example: Oak Ridge Boys member spent 30,000 to treat a cow with a flesh-eating bacteria (mycoplasma) to keep it alive so it could nurse its calf.
- The whole leg musculature was affected, with only bone left after treatment.
- Mycoplasma is an opportunistic bacteria infiltrating the skin.
- Used as an analogy for how cancer destroys good tissue.

Cancer cells are abnormal cells: spindly, weird-shaped, and opportunistic.
They infiltrate and destroy good tissue in organs like the kidney, heart, or spleen.
They take over and kill good cells.

Tumors are classified by the type of tissue they arise from:
- Epithelial Tissue: Adenomas or carcinomas.
- Mesenchymal Tissue: Fibromas and fibrosarcomas.
- Round Cell Tumors: Lymphomas and mast cell tumors.
- Melanomas: Tumors of pigmented cells (melanin).

Melanomas are linked to skin pigmentation and sun exposure.
People of Scotch-Irish descent are at higher risk.
Freckles are changes in melanin skin pigment and can turn into melanomas with excessive sun exposure.

Dogs:
- Mast cell tumors
- Lymphomas
- Lipomas (fatty tumors)
- Hemangiosarcomas (typically splenic)
Cats:
- Lymphoma (especially gastrointestinal)
- Squamous cell carcinoma (especially in white cats around the oral cavity and eyes)
- Fibrosarcoma (injection site tumors from the feline leukemia vaccine)

Solid white cats are prone to squamous cell carcinoma around the eyes and oral cavity.
Solid white cats with blue eyes are often deaf (90% likely).
Genetic predisposition to deafness due to recessive trait.

Abnormal growths on the spleen surface.
Common in golden retrievers and Labradors.
Splenectomy can be curative; dogs can live without a spleen but have a higher risk of tick-borne diseases.

Develops as finger-like projections that spread aggressively.
Vaccination site is crucial: feline leukemia vaccine (FELV) should be given in the left rear limb.
- Rabies vaccine is given in the right rear limb to differentiate reactions.
Vaccinating lower on the leg allows for amputation if a tumor develops.
Personal opinion: the lecturer does not vaccinate their own cats against feline leukemia due to the risk of fibrosarcoma.

Fine Needle Aspirate (FNA):
- A needle and syringe are used to extract cells from a growth.
- Cells are placed on a slide, stained, and examined under a microscope.
Biopsy:
- The entire growth is removed and sent to a pathologist for analysis.
Physical Exam and History: Gathering information about the animal's health and lifestyle.
Staging:
- Involves assessing lymph nodes, thoracic radiographs, and blood work (CBC and chemistry).
Rats as Tumor Factories:
- Tumor size is measured in lab animals.
- Endpoint is reached when the tumor affects the animal's quality of life.
- Staging is common to assess the tumor's progression.

Surgical Removal:
- Suitable for tumors in locations like the spleen.
Chemotherapy:
- Typically done at referral centers or vet schools.
- Toxic and requires special handling to avoid exposure.
Radiation Therapy:
- Used in cases like lung metastasis.
Palliative Care:
- Focuses on supportive care and quality of life.
- Managing pain and ensuring the animal's comfort.