Cancer is the uncontrolled growth of cells. The cancerous
cell mass is called a tumor or neoplasm. Cancers can be harmless (benign)
or malignant. Cancer cells grow more rapidly than normal, healthy cells.
Of the cancerous cells, benign tumors tend to grow less quickly, remain
localized to a distinct mass, and can be cured by surgical removal.
Malignant tumors tend to grow rapidly, invade surrounding tissues, spread
to other parts of the body (metastasize), and are not as easily removed by
Most tumors result from unknown causes. Other possible
causes of cancer include exposure to cancer-causing agents such as
ultraviolet radiation (sunlight), x-rays, cigarette smoke, or viruses
(feline leukemia virus, feline sarcoma virus).
From the American Veterinary Medical Association:
- abnormal swellings that continue to grow
- sores that do not heal
- lumps in the breast area
- offensive odor
- difficulty breathing
- difficulty eating or swallowing
- difficulty urinating or defecating
- loss of energy or reluctance to exercise
- loss of appetite, weight loss
- lameness or stiff movement
- bleeding or discharge from any body
opening (mouth, nose, urinary tract, vagina, or rectum)
Health history, clinical
signs, physical exam, and X-rays may identify the presence of a tumor, but
definitive diagnosis of cancer requires identification of the tumor cells
under a microscope. The cells can be obtained during a biopsy,
where a small sample of the cells is collected. A biopsy is very
important. Even experienced veterinarians cannot always tell the
difference between a developmental problem, inflammatory condition, and a
tumor on the basis of a physical examination alone. This is
especially true with a small tumor. Since proper diagnosis and treatment
are so important in cancer, and a misdiagnosis could either delay
treatment or result in unnecessary treatment, the benefits of a biopsy and
microscopic identification of the suspected tumor cells far outweighs the
very small risks associated with performing a biopsy. A small tumor may be
biopsied and removed all at once. This is called an excisional
biopsy because the tumor has been excised (removed) from the
body. A larger tumor may require an incisional
biopsy where an incision is made and a small edge of the tumor
is removed. Another biopsy technique is called fine-needle
aspiration, where a needle is inserted into the tumor and a
sample of cells are drawn into a syringe. Biopsies are often done under
anesthesia and ultrasound may be used so the doctor can guide the needle
to the proper location.
Since prompt treatment is critical, a "let's wait and see what
happens" approach is no longer considered acceptable when a lump is
found. If there is even the smallest chance that the lump could be a
cancerous tumor, a biopsy should be performed. You don't want to panic
every time you feel a small lump on your pet, but if the lump has grown
quickly, is changing, or is somehow unusual, you should get it checked
out. Older dogs commonly have benign fatty lumps (lipomas) and your vet
can examine them and tell you what they are.
The specimen collected during a biopsy is sent to a pathologist who
identifies the type of tumor, whether it is benign or malignant, and
describes different characteristics of the tumor cells. These
characteristics help in determining how advanced the cancer is, whether it
is localized or has invaded other tissues, and how well your pet may
respond to treatment.
Like most other diseases, early detection and treatment
are very important. Cancer treatments vary depending on the type and stage
of cancer, and there are far too many specific treatments to describe
here. We've described the general forms of treatment below. Multiple forms
of treatment are often used.
surgical removal the the tumor and other involved tissues.
therapy: some form of radiation is targeted to the cancer cells and is
believed to damage the DNA and interfere will cell replication. For
example, hyperthyroidism in cats is often treated with radioactive iodine,
which is taken up by the overactive thyroid gland and destroys it.
administration of a drug that destroys tumor cells. These drugs are called
cytotoxic agents. Anti-cancer drugs have various side effects because they
do not act just on the tumor cell, but on all cells. They tend to
act on rapidly growing cells (tumor cells), but healthy cells of the bone marrow
and digestive tract are also rapidly growing cells and they may be
effected. Side effects in pets are usually much less severe than you hear
about in humans (vomiting, hair loss) and most pets tolerate chemotherapy
very well. Blood tests to monitor CBC, liver, and kidney function
are often performed during the course of chemotherapy to be sure the
non-target cells are not being damaged too much.
freezing the tumor tissue to death, usually using liquid nitrogen. Tumors that may be treated with cryosurgery are usually on the
surface of the body and include those involving the skin, oral cavity, ears,
heating tumor cells to kill them or their blood supply. Hyperthermia
is often used with other treatments such as radiation therapy or
therapy: lasers (powerful light sources) can be used as a type
of scalpel to separate the tumor tissue from healthy tissue. The use
of a laser reduces blood loss and contamination of the surgical area, and
decreases the potential for spreading tumor cells. Laser therapy may also
be used in a form of treatment where first a drug is given that sensitizes
the tumor cells to light, then the laser is used to irradiate the tumor
with light, which activates the drug and the tumor tissue is
boosting the immune system so the body can better respond to destroy the
tumor tissue. It is usually used with surgery, chemotherapy, or
radiation therapy. Tumors treated by immunotherapy are usually small and
Considerations for Treating Diabetics
The decision to treat a
cancer is a difficult one, but just because your pet is diabetic does not
mean cancer therapy should not be considered. Many diabetic pets have
successfully undergone treatment for cancers.
Depending on the type and stage of cancer, treatment may cure your pet of
cancer. In other cases, treatment may not be able to cure your pet, but
may be able to alleviate many of the problems associated with the cancer,
improve your pet's quality of life, and give you many more years with your
The long-term prognosis, overall health of your pet, age, severity and
duration of debilitation that will result from treatment, post operative
care, and cost are all factors that should be considered when deciding
whether or not to have your pet undergo cancer therapy.
When you discuss these things with your vet, be sure to keep in mind that
your pet has diabetes. Minimizing stress and keeping the diabetes as well
controlled as possible will help your pet's healing process. If there is a
loss of appetite or decreased activity during treatment and recovery, your
pet's insulin dose may need to be decreased.
Questions for your vet
- If your pet is having surgery, what will
you have to do about feeding and insulin the night before surgery?
- After surgery, how long of a recovery time
is typical? Will someone be
monitoring your pet's bg to be sure it isn't too high or low?
- What types of side-effects should you
expect from the treatment?
- How severe are the side
- What do you do if the side effects seem
severe or if your pet's diabetes becomes very uncontrolled?
- Will the chemotherapy drug or other
treatment damage the
pancreas and make the diabetes worse? This may be a side-effect you
have to accept, but it would be nice to know in advance if this is
something you should expect.
- If you want to use dietary supplements,
herbal remedies, or any other non-traditional therapies during the
treatment or recovery period, be sure to ask your vet if they will
effect the diabetes or the cancer treatment.
diabetes and Cancer
would like to share your pet's experience with diabetes and cancer, please
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There are several excellent resources on the Internet for pets with cancer
Living With Cancer: A Pet Owner's Resource
Paperback - 142 pages Dr. Robin Downing, a veterinarian who had to confront a cancer diagnosis in her dog, Murphy, found there was no one source for all the questions she faced.
Her book is a complete guide to treatment and care. Written with the positive but realistic view that cancer does not always mean death,
she answers many questions in a comprehensive and caring manner.
There is a glossary of terms common to cancer discussions and treatment.
Rose: Diary of a Very Special Love by Martin Scot
Kosins (August 1996). From the days of Maya's
youth to the sad and courageous years of her decline, this exhilarating memoir captures
the magical bond that can grow between humans and animals.
If you know someone
who is caring for a "special needs" pet or who has
recently lost a pet, this is a wonderfully
that you can inscribe.
Updated January 2004
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