Skin Cancer in Dogs
Skin cancer in dogs covers a broad range of tumors that are characterized by an uncontrolled growth of cells. They can include the growth of skin cells, glands, hair follicles and even fat and other tissues. Skin cancer does not usually include cancers that metastasize to the skin from other cancerous sites in the body since they do not originate from the skin.
Causes
As the largest organ in the body, it is not surprising that the skin is also the most frequent site of cancer in the dog. However, most skin tumors are benign. Skin cancer in dogs usually appears in dogs that are six to 14 years old. However, there are a few kinds of skin cancer that can appear in younger dogs.
The precise causes of skin cancer are not known. However some dogs do seem to be more likely to get skin cancer than others. Dogs of the following breeds seem more likely to get skin cancer: Scottish Terriers, Basset Hounds, Boxers, Weimaraners, Kerry Blue Terriers, Bullmastiffs, and Norwegian Elkhounds.
Dogs that are exposed to the sun a great deal may have a higher incidence of squamous cell carcinoma and hemangioma. Dogs with lighter colored coats and with thin hair, or without hair, who spend a great deal of time in sunlight seem to have a higher risk of developing these kinds of skin cancer. It is also believed that their could be a genetic element in the risk for some kinds of skin cancer.
There are essentially four kinds of skin cancer, depending on the kind of cell type that becomes cancerous. They are:
- Epithelial tumors which involve the skin, the glands, or the hair follicles.
- Mesenchymal tumors develop from cells that surround or support the skin. These include fat, connective tissue, blood vessels, and nerves.
- Round cell tumors appear round under the microscope. They include lymphosarcoma, mast cell tumors, histiocytomas, plasma cell tumors, and transmissible venereal tumors.
- Melanomas derive from melanocytes. These are the cells which give the skin pigment.
Diagnosis
The most common tumors in dogs are lipomas, mast cell tumors, sebaceous gland adenomas/hyperplasia, and papillomas. Skin cancer usually appears as a lump in the skin, or beneath the skin. Or it may appear as a sore which doesn’t heal. A dog with skin cancer may feel uncomfortable or itchy. They may chew or scratch the area in question. Depending on the cancer, the area may be red or it may appear flaky.
If you think that your dog may have some kind of skin cancer it is always best to take him to the veterinarian to find out for sure. Early diagnosis and treatment are best for your dog.
In addition to a physical examination, your veterinarian will need to perform some tests in order to determine if your dog has skin cancer. The tests will depend on the kind of skin cancer suspected and how advanced it might be. Tests which your vet may need to perform include:
- Cytological exam, or a microscopic examination of cells from the tumor. This may involve doing an aspiration of the tumor or a small biopsy to remove some cells.
- Biopsy to remove a small portion of the tumor to check the cells for cancer. This is the most accurate way to determine if your dog has a skin tumor. There are several different kinds of biopsy. Your vet will determine which one is most appropriate for your dog’s case.
- Complete Blood Count (CBC)
- Serum chemistry panel to evaluate your dog’s body chemistry and overall health.
- Urinalysis
- Chest x-rays to see if the tumor has metastasized to your dog’s lungs. Skin cancer often spreads to a dog’s lungs.
Your vet will need to rule out many diseases and infections which can cause lumps, sores, hair loss, itching, flaking, and redness of the skin. Some abcesses and infections can look like skin tumors or carcinomas. Some immune mediated diseases can cause ulcers and sores that may appear cancerous. These diseases may also have to be ruled out. In some cases cysts and ordinary traumas may look like certain kinds of skin cancer.
Treatment
Treatment for skin cancer in dogs depends on the kind of tumor found and how developed it is. Surgery is often the first choice of treatment if the tumor hasn’t spread and it can be entirely removed without damaging any other tissues. Surgery may also be suggested to make the tumor smaller so it can be better treated with other options. If your dog has a benign tumor, surgery will usually end the problem. Surgery may cure a malignant tumor, too, but you will need to watch for recurrences.
Radiation is often considered if surgery cannot be used to remove the whole tumor. Radiation therapy usually involves several treatments over several weeks.
Chemotherapy is an option if the cancer has spread to other organs or tissues. Chemotherapy is most often used for lymphosarcoma and mast cell tumors.
Cryosurgery is sometimes considered if the tumor is very small. This procedure freezes the tumor and the skin next to it with liquid nitrogen.
Photodynamic therapy is an option in some cases. This is a new treatment in which a dye is injected into the dog’s bloodstream. The dye congregates in the cancerous cells and a laser is used to excite the cells and kill them.
Long Term
You should check your dog’s skin regularly for any new lumps, bumps, and sores. If there are unexplained bumps or sores that don’t heal, you should take your dog to see the veterinarian.
You should avoid exposing your dog to the sun for prolonged periods of time, especially if he has lighter-colored coat, thin coat, or is a hairless breed.
Following any surgery for skin cancer in dogs you will need to watch the area for problems such as redness, swelling, and discharge.
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