It all starts with a normal cell, that goes bad.
The cells divide and multiply as the animal matures to adulthood. When an animal has stopped growing, cells stop multiplying—except for some cells in the bone marrow, skin, and intestines. Cancer occurs when cells that are supposed to have stopped multiplying, continue to do so. This results in a tumor. There are two kinds of tumors, benign and malignant. When benign tumors are biopsied or removed, the cells from the tumor closely resemble the cells of the normal tissue it was taken from. These tumors are not cancerous. Malignant tumors have cells that do not resemble the tissue they were taken from, they are cancer. They can then spread or metastasize to other areas of the body or regrow at or close to their original location.
COMMON SIGNS OF CANCER IN SMALL ANIMALS
1. Abnormal swellings that persist or continue to grow
2. Sores that do not heal
3. Weight loss
4. Loss of appetite
5. Bleeding or discharge from any body opening
6. Offensive odor
7. Difficulty eating or swallowing
8. Hesitation to exercise or loss of stamina
9. Persistent lameness or stiffness
10. Difficulty breathing, urinating, or defecating
Cancer can sometimes be as obvious as a bump under the skin or a wound that refuses to heal. More often, it is hidden where we cannot see it without the aid of x-rays or ultrasound. Most animals are not presented because the owner suspects cancer. They are presented for many different reasons—they just haven’t felt well, not eating very much, or have just been lying around. Diagnosis starts with a physical exam and a bloodwork. It might then be recommended to do x-ray pictures or an ultrasound. If a tumor is found, a biopsy may be done to determine what kind it is.
CARCINOMA OR SARCOMA?
Carcinomas originate from the skin, eye, nervous system, lungs, liver, pancreas, gastrointestinal system, and salivary glands. Sarcomas originate from the heart, blood vessels and cells, musculoskeletal system, bones, tendons, fat cells, and urogenital tract. Leukemia is also a type of sarcoma. A tumor may start out as a carcinoma or sarcoma in one location, but it can metastasize to another part of the body.
TYPES OF CANCER:
Cats and dogs are prone to different types of cancers.
Cats: Cats are more likely to develop lymphosarcoma, squamous cell carcinoma, or mammary cancer.
Mammary cancer occurs almost exclusively in unspayed pets. Fortunately, most people know to spay or neuter their pets, so this type of cancer is not seen as often.
Squamous cell carcinoma is a skin cancer that is usually seen as lumps, open wounds, or rough areas, especially on white or other light-colored cats.
Lymphosarcoma is a cancer that affects the lymph tissue of any organ.
VACCINE SARCOMAS IN CATS
In recent years there has been an increased awareness of sarcomas in cats induced by injections. These occur in some cats after they have been injected with a vaccine, antibiotic, or other medication. A bump will appear that will not subside in a few weeks. A biopsy can confirm if it is a tumor. Fortunately, these sarcomas are becoming rarer as more is learned, vaccines and drugs are improved, and vaccine protocols are changed.
Dogs: We see more dogs with cancer than we do cats. Lymphosarcoma and mammary cancer are seen in dogs, as well as cats. Some common types of cancer seen in dogs are hemangiosarcoma, mast cell tumor, osteosarcoma, and transitional cell carcinoma.
Hemangiosarcoma in the dog and is a very aggressive cancer that usually involves the spleen, but can be near the heart and other sites. These dogs are usually presented feeling very lethargic and not eating. They are usually older, a larger breed dog, and were feeling fine until just recently. The prognosis is not good for hemangiosarcomas.
Mast cell tumors are skin tumors that appear as raised bump(s) which may eventually become open wounds all over the body. Most of these dogs are not bothered by the bumps, but the disease will eventually be fatal if untreated.
Osteosarcoma is a tumor involving the bones. It accounts for about 90% of all bone tumors. It is primarily found in large breed dogs. This is treatable only if found early and has not spread.
Transitional cell carcinoma can be presented as dogs that are having trouble urinating, as it affects the bladder. It can also affect the prostrate and the kidneys. Surgery can be used to treat this depending on the location of the tumor and chemotherapy has seen some very promising results.
After a diagnosis has been made, there are three main choices for treatment.
Surgery can be curative if the cancer has not spread and the excision is complete.
Radiation is used for tumors that are not good surgery candidates or in combination with surgery. The radiation strikes at the quickly dividing cells, killing them.
Chemotherapy is the third option. It is can be used alone or in combination with surgery and radiation. Chemotherapy is not usually considered a total cure.
Choices for treatment vary depending on the type of cancer. Certain situations require a combination of treatments to try to eradicate the tumor. The prognosis is always guarded for a complete cure. Survival rates will depend on the tumor type, when or at what stage it was found, and the treatment choice.