Cancer
Cancer in dogs can affect everything from the skin to the
bones. The disease is caused by uncontrolled cell growth and can take one of
two forms: benign (does not grow in an unlimited, aggressive manner, does not
invade surrounding tissues and does not spread to other parts of the body) and
malignant (meaning it enters healthy tissues, grows aggressively and spreads to
other areas of the body.) Since some cancers grow slowly while others develop
more quickly, be sure to consult your veterinarian as soon as possible if you
notice anything unusual.
Types of Cancer
There are several different types of cancer in dogs. The
following are some of the most common, including their symptoms and treatments:
* Hemangiosarcoma
(HSA)- An aggressive, malignant cancer that arises from the blood vessels and
mostly affects the spleen, heart or skin. The skin form is associated with sun
exposure and white haired breeds are at greater risk. The lesions look like
dark red or black growths on the skin and should be removed immediately since
1/3 will spread internally. Hemagiosarcoma of the spleen and heart usually
present with acute collapse/ weakness and pale gums due to bleeding of the
tumor. German shepherds, golden retrievers, boxers and English setters seem to
be predisposed. Surgical removal of the spleen and biopsy is needed to diagnose
HAS, since the mass may benign (hemangioma or hematoma). Surgery to remove the
heart mass or open up the lining of the heart is only palliative and often the
mass is not resectable. While early and aggressive treatment, including
chemotherapy, can prolong your dog's life, complete remission is rare.
Cutaneous
Histiocytomas - Small, round benign tumors that can appear anywhere on the
body's skin, but are most common on the head, ears and neck of dogs less than 3
years of age. They usually regress in 2-3 months, however, if the tumors bother
your dog, they can be surgically removed. This tumor has been reported to be
the most common skin cancer and the most commonly observed form of cancer
overall.6,7
Lymphoma (LSA) - A
common, malignant cancer (about 10-20% of all cancers in dogs) that occurs in
the lymph nodes, spleen, liver and other organs, affecting primarily
middle-aged and older dogs. Certain breeds like rottweilers, Scottish terriers
and golden retrievers are at increased risk and there is also some speculation
that it may run in families. The tumors in the lymph nodes appear as swellings,
but other symptoms vary depending on the portion of the body involved: the
gastrointestinal form of this cancer causes vomiting, diarrhea and weight loss,
the chest form leads to shortness of breath and muffled heart sounds, and the
skin form causes itchy red lumps to appear on the skin and inside the mouth.
Biopsies, X-Rays and ultrasounds are used to diagnose lymphoma. Once diagnosed
lymphoma should be staged in order to determine best course of treatment and
provide a prognosis. Treatment often consists of chemotherapy +/- surgery. Some
veterinary hospitals are now offering a bone marrow transplant, but the cost
(around $20,000) will likely prohibit most us from pursuing it. A consultation
with a veterinary oncologist can determine the best course of treatment, which
can sometimes add a year or more to a dog's life.
Mammary Cancer -
Most common cancer in female dogs and predominantly affects older female dogs
between five and ten that have not been spayed. German shepherds, cocker
spaniels, poodles and terriers are overrepresented. Half of these tumors are
malignant and half of these have spread at the time of diagnosis. The tumors
can affect one or more of the mammary glands along the belly of your pet. They
can be a single small mass or be multiple large ulcerated masses. Malignant
tumors usually grow rapidly, and benign tumors are typically slow growing. A
biopsy and microscopic investigation will determine if the tumors are benign or
malignant. Prompt surgical removal of any mammary tumor is recommended. If
caught early enough, surgical removal of the tumors can completely eliminate
over 50 percent of malignant cases. Spaying is also recommended if not already
done since 50% of malignant tumors and some benign tumors have receptors for
female hormones. Early spaying (before the first heat) reduces the risk of
developing mammary cancer. Sometimes chemotherapy is also used in the treatment
of some mammary cancers. Prognosis depends on type of cancer, size of the mass,
extent of spread, ulceration, how fast it grows and the biopsy results.
Mast Cell Tumors
(MCT)- These are a common skin tumor (20% of all skin tumors in dogs) found
anywhere on the skin, especially the trunk. boxers, Boston terriers,
bullmastiffs and English setters are predisposed. MCT vary in appearance and
can be smooth, bumpy or ulcerated. They can also get bigger or smaller over a
short period of time, especially when touched due to the compounds in MCT
(histamine and heparin) causing redness and swelling. Most MCT are locally
invasive and often difficult to remove. These tumors are graded I-III, based on
their behavior (invasiveness, how well differentiated it is, how quickly it is
dividing etc) and the higher grades are staged. MCT typically spread to lymph
nodes, liver, spleen and bone marrow so staging requires blood work, x-rays,
ultrasound, lymph node aspirates, bone marrow aspirates. Surgical removal +/-
radiation therapy is the main treatment and require wide margins. Chemotherapy
is sometimes used but response is unpredictable. Prognosis is good for grade I
and II and the prognosis for dogs with grade III is guarded. Dogs that develop
MCT are likely to develop more, therefore need to be watched closely.
Osteosarcoma
(OSA)- Most common bone tumor in dogs. It is an aggressive, malignant, highly
metastatic bone tumor most often occurring in the bones around the shoulder,
wrist and knee but can develop in any bone. It primarily affects older large or
giant breed dogs, with great danes, Saint Bernards, great Pyrenees,
Newfoundlands, Bernese mountain dogs and Irish wolfhounds being at greatest
risk. The tumors usually produce pain, lameness and swelling in the affected
limb. Sometimes they present as a fracture. A biopsy is done to identify the
cancer and because of the high metastatic rate, chest x-rays are also
indicated. Other tumors can mimick OSA like Chondrosarcoma, Squamous Cell
Carcinoma and Synovial Cell Sarcoma. Fungal infections can have similar
symptoms, so fungal titers should also be done if there is possible exposure.
Treatment options include amputation, radiation, chemotherapy and pain
medications depending on if you want to alleviate pain or try for a cure.
Prognosis depends on many factors and survival times vary from 3 months to 2
years.
Cancer can be a devastating diagnosis. Even if your pet has
been diagnosed with cancer, fight it with the positive power of nutrition.
Nutrient rich foods that will give your dog the best opportunity to be healthy,
like Prescription Diet n/d can create a powerful platform from which your dog
can fight cancer.
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