Diagnosis and Management of Cancer in Horses

Question 1

benign

Answer 1

tumor that lacks the ability to metastasize

Question 2

malignant

Answer 2

tumors that have the ability to metastasize

Question 3

common skin and subcutaneous tumors with horses

Answer 3

sarcoid, squamous cell carcinoma, lymphoma

Question 4

what 2 types of neoplasia are age independent in horses?

Answer 4

sarcoid, lymphoma

Question 5

Sarcoids

Answer 5

Sarcoids are the most common tumor of horses and is a non metastatic soft tissue sarcoma affecting the skin.

Question 6

what do sarcoids look like on histopathology?

Answer 6

On histopathology theres a hyperplastic epidermis, spindle cells form rate pegs that extend deep into the tissue, sarcoid cells often extend up to 2 cm away from the gross tumor.

Question 7

what are the 4 different sarcoid types?

Answer 7

nodular, verrucous, flat/occult, fibroblastic (aggressive)

Question 8

Sarcoids pathogenesis

Answer 8

1. bovine papilloma virus: virus inactivates p53 gene which is a gene that stimulates apoptosis
2. genetic predisposition: familial tendency identified in swedish warmblood and quarter horses

Question 9

Squamous cell carcinoma

Answer 9

The most common cancer of the globe and adnexal structures that has a tendency for malignancy especially if on the prepuce/penis. These are often a fleshy and cobblestoned mass that have a secondary bacterial infection.

Question 10

Squamous cell carcinoma pathogenesis

Answer 10

UV radiation, non pigmented skin, increasing age, equine papilloma virus infection causing damage to the p53 gene allowing for unchecked cell proliferation.

Question 11

what breeds are genetically predisposed to SCC?

Answer 11

halflingers, belgians, clydesdales, and shires

Question 12

Melanocytic Tumors

Answer 12

Tumors arising from the malignant transformation of normal melanocytes. 80% of gray horses will develop melanomas.

Question 13

when should you remove melanocytic tumors?

Answer 13

Try to remove it before it becomes a problem and check for mets first in the abdomen and spinal cord. Remove the tumors when small if possible

Question 14

where do melanocytic tumors metastasize?

Answer 14

local lymph nodes, abdominal cavity, brain and spinal cord

Question 15

Lymphoma

Answer 15

Malignant neoplasm of lymphocytes. Cutaneous lymphoma is relatively common and in the early stages of disease is confined to the skin. As the disease progresses there will be hepatosplenic infiltration, leukemia, IMHA, IMTP, Agammaglobulinemia, hyperglobulinemia.

Question 16

what is the gold standard for diagnosing neoplasia?

Answer 16

Biopsy, allowing for appropriate ID and tx; and accelerate cell proliferation and therefore must be followed by treatment.

Question 17

diagnostic techniques for lymphoma

Answer 17

IMHA, Lymphocyte phenotyping, IgG and IgM quantification, serum protein electrophoresis, hypercalcemia

Question 18

what margins should you taken when removing a tumor?

Answer 18

basal cell carcinoma, mast cell tumor: 0.5cm

SCC, cutaneous lymphoma, melanoma: 0.5 - 1cm

Sarcoid, fibrosarcoma: 1-2 cm

Question 19

you need AT LEAST ___ cm of normal tissue on histopathology at all margins to call it clean

Answer 19

you need AT LEAST 0.5 cm of normal tissue on histopathology at all margins to call it clean

Question 20

Cryotherapy

Answer 20

Temps -20C result in cellular destruction and is cheap and easy but not always effective

Question 21

CO2 Laser

Answer 21

CO2 laser is for superficial disease only (0.03mm) and is often used in combination with chemotherapy in tumors that can’t be sharply resected.

Question 22

Topical Treatments are only effective for __ disease on a nice horse in an easy location with a compliant client. __ and __ are the most researched.

Answer 22

Topical Treatments are only effective for superficial disease on a nice horse in an easy location with a compliant client. 5- fluorouracil and imiquimod are the most researched.

Question 23

5 fluorouracil

Answer 23

A pyrimidine antagonist that inhibits DNA synthesis and is proven effective for treatment of SCC and superficial lesions of the prepuce. Tx 1x week for 5 weeks.

Question 24

Imiquimod

Answer 24

An immune response modifier that effects the innate and cell mediated immune response causing an intense inflammatory response at the area of application. It should be applied 3x/week until complete resolution or 32 wks.

60% of sarcoids had total resolution in 8-32 weeks

Question 25

Topical chemotherapy - mitomycin C ophthalmic ointment

Answer 25

Inhibits RNA and alkylates DNA resulting in chromosomal breakage. Excellent treatment option for ophthalmic SCC.

Question 26

intratumoral chemotherapy

Answer 26

cisplatin, bleomycin

This is for tumors that are < 10cm or after surgical debulking. intratumoral cisplatin causes apoptosis of cells by cross linking with purine bases and interfering with DNA repair

Question 27

Electrochemotherapy

Answer 27

Injection of a cytotoxic chemotherapy agent followed by electrical current. Electric current increases cell permeability, increasing the intracellular uptake of a cytotoxic agent.

Question 28

Radiation

Answer 28

Causes double stranded DNA breaks resulting in broad spectrum therapy

Question 29

oncept vaccine

Answer 29

vaccine developed for the treatment of canine melanoma

Question 30

tigilanol tiglate

Answer 30

remove top of tumor base and then inject with immunotherapy and it heals over the next 1-3 months

Question 31

chemotherapy goal

Answer 31

Kill the largest fraction of tumor cells possible without causing unacceptable toxicity in normal tissue

Question 32

Corticosteroids for chemotherapy

Answer 32

Induces the killing of hematopoetic cancer cells through apoptosis. Pulse dose therapy is ideal and you should continue admin at the lowest possible dose.

Question 33

what treatment should you offer first?

Answer 33

the most aggressive and most effective