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Pet Article
DOGS, CATS AND TUMORS
Lumps can be very common occurrences in our dogs and cats, especially in geriatric ones.
Approximately 30 per cent of all tumors found in dogs and cats occur on the skin. As a pet
owner finding a lump on our pet, we should ask ourselves the following questions: Has the
lump appeared suddenly, or has it been there a while? Has the lump stayed the same in
consistency and appearance, or has it changed? Does the lump seem to separate from
underlying tissue or is it attached? Is there only one lump or have you found multiple
similar lumps? Have there been changes in your pets behavior, such as eating less, losing
weight, vomiting, diarrhea, or lethargy? By answering these questions may help your
veterinarian evaluate the seriousness of the lumps presence.
Lumps are often benign accumulations of fat, known as lipomas. However, many lumps
are not lipomas, so all should be evaluated for the possibility of a more aggressive
malignancy. In general, many benign lumps may grow slowly or not at all, and remain unchanged
for many months to even years. However, many malignant lumps grow rapidly and may infiltrate
into the underlying tissue.
One of the easiest ways to figure out if a lump is benign or malignant is for your veterinarian
to take a fine needle aspirate. These are the same needles that are used to give vaccines,
and they just extract a few cells so your veterinarian can take a look at them under a
microscope.
Many skin tumors, benign or malignant, can be cured with surgery. However, skin tumors
could be just the tip of the iceberg. Diagnostic tests may be needed to determine whether
your pet's lump is a manifestation of a more widespread disease.
The most common malignant skin cancer in the dog is mast cell tumor. Mast cells are
normal cells in the body that serve a normal defense mechanism. When you get bit by a
mosquito, it?s the mast cells that instigate the inflammatory response that causes the
production of a red, itchy, hive. Mast cells also mediate most allergic diseases such as asthma
and food allergies.
If the normal mast cell undergoes a malignant change, a mast cell tumor may be produced.
In the dog, mast cell tumors may be benign; however, many tumors possess varying
degrees of malignancy, ranging from local reoccurrence following surgical removal to
aggressive systemic disease, which may be fatal. The potential for mast cell tumor
aggressiveness may be determined by a biopsy. Other factors are also important in
predicting the biologic nature of mast cell tumors.
Although mast cell tumors primarily affect the skin, they have the potential to spread to
other areas of the body. Therefore, it is important not only to address the skin tumor, but
also to fully evaluate patients for systemic spread (metastasis) with blood work, thoracic
radiographs, and abdominal ultrasound. If there is no evidence for tumor metastasis,
surgical removal of the mast cell tumor may cure the problem. If complete surgical removal
of the mast cell tumor is not possible, radiation therapy or systemic chemotherapy should be
considered.
In the cat, mast cell tumors of the skin are generally benign, and surgery usually cures the
problem. Systemic spread from a primary skin mast cell tumor is rare in the cat, unlike the
dog. However, some cats may manifest with a distinctly different type of mast cell tumor
that primarily affects internal organs, such as the spleen, liver, and bone marrow. This type
of mast cell cancer is known as visceral mastocytosis and is much more aggressive than
mast cell tumors of the skin.
When you notice a lump or bump on your pet, it is best to have a veterinarian look at it
soon. Many pets have lumps all their lives that remain benign, but if a lump is malignant,
your pet has a better prognosis if treated early. Skin cancers are quite common, and many
are treatable and curable.
If you find a lump on your pet, contact your local veterinarian.
Mark Woodcock
1 Flea Control
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