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Cancer (neoplasia) is a transformation of normal cells into abnormal malignant cells, and it can take many forms. Some involve solid masses, or
tumours, while others involve the blood or bone marrow in leukaemia. Cancer can develop in virtually any organ or body system.
In addition, some cancers spread or metastasise to other areas of the body. They can spread to nearby tissues, or invade the blood stream or lymphatic system. Cancer commonly
metastasises to the lung. The exact symptoms, treatment and prognosis vary with the specific
tumour type and situation. |
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| Canine Cancer: What Are The Warning Signs? |
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Dogs get many of the same types of cancer as humans; frequent exams and tests help detect cancer before it is too late for treatment.
Signs of Cancer
Not too long ago, when a dog owner learned that a pet had cancer, it meant a death sentence for the animal. But, thanks to advances in cancer research, things have changed.
Cancer is an uncontrolled growth of cells on or within the body. It may be localized, or it may invade adjacent tissues and spread throughout the body. Cancer is common in pet animals, and the rate increases with age. Dogs get cancer at roughly the same rate as humans, while cats get fewer cancers. Cancer accounts for almost half of the deaths of pets over 10 years of age.
Unfortunately, the cause of most cancers is not known and therefore prevention is difficult. One type of cancer, breast cancer, is largely preventable with early spaying. Fifty percent of all breast tumors in dogs are malignant. Spaying your pet prior to the first heat cycle will greatly reduce the risk of breast cancer.
Cancer can occur in almost any location or body system – for example areas such as the skin, gastrointestinal tract (stomach, bowels), urinary system (kidney or bladder), blood, nervous system (brain tumors) and bones.
Different types of tumors can grow in each location of the cancer. A cellular diagnosis is needed to determine the “type” of cancer. For example, cancer of the skin can be due to basal cell tumors, mast cell tumors, lymphosarcoma and fibrosarcoma. Each tumor type within a location has a different treatment and prognosis.
Signs of Canine Cancer
Do you know the signs of cancer in dogs? Dogs get many of the same types of cancer as humans, and frequent physical exams and diagnostic tests help detect cancer before it is too late for treatment. Some common types of cancer in dogs are:
Skin tumors. Skin tumors in dogs are rather common. Melanomas, lipomas, basal cell tumors and mast cell tumors are the most often diagnosed. All skin tumors – lumps or masses of any sort – should be examined by your veterinarian.
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Lymphoma. This form of cancer is common in dogs. Lymphoma can affect the digestive system, resulting in lethargy, vomiting and diarrhea. It can also affect the liver resulting in lethargy, vomiting and a yellow tinge to the gums and skin. Lymphoma can also affect the chest, causing coughing and difficulty breathing. More
info....
Mammary gland tumors. These tumors are more common in the older female dog that has not been spayed. About 50 percent of all tumors in dogs are mammary gland tumors. Of those, about ½ are malignant. Typically, a lump is felt in the breast tissue. Although they are most common in intact dogs, they can also occur in spayed dogs.
Abdominal tumors. Abdominal tumors are common, but it is difficult to make an early diagnosis. Some examples include hemangiosarcoma, mast cell tumors, lymphoma and prostate cancer. You should be aware of any weight loss, weakness, pale gums, protracted vomiting, continual diarrhea, and/or abdominal enlargement and see your veterinarian if these signs occur.
Testicular tumors. This type of tumor is the second most common tumor of intact male dogs. Signs are usually one large testicle and one normal sized testicle. If malignant, the cancer can spread throughout the body, resulting in weakness, lack of appetite and weight loss.
If you notice any of the symptoms, consult with your veterinarian. If found early, most of these cancers can be cured with surgery, chemotherapy, radiation therapy, or a combination of the three, and early diagnosis will aid your veterinarian in delivering the best care possible.
What to Watch For
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Any lump or mass that appears to be increasing in size
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Any sore that does not heal
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Change in bowel or bladder habits
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Difficulty urinating or defecating
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Unexplained bleeding or discharge from any body
opening
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Loss of appetite
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Weight loss
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Difficulty breathing
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Persistent lameness or stiffness
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Offensive odor
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Difficulty eating or swallowing
Pet
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Non-Cancerous Tumors in Dogs |
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Non-Cancerous Tumours in Dogs
A hard lump on or under your dog's skin is alarming, but may not be cancer. Many are actually non-cancerous growths such as lipomas, cysts and histiocytomas. While testing is required to verify that these are indeed non-cancerous
tumours, the majority of growths that occur on dogs are benign
tumours that may not even require removal.
Lipomas (Fatty Tumours)
Lipomas, or fatty tumours, are the most common non-cancerous tumour found in dogs. Lipomas are deposits of fatty tissue under the skin that are separated from surrounding body fat by a fibrous covering.
Fatty tumours are usually round and smooth. Lipomas are not usually painful, but when they become so large that they interfere with a dog's comfort or mobility they should be removed surgically. Fatty
tumours are most common in obese female dogs.
Because some fatty tumours are cancerous, a needle biopsy of the growth may be performed. A needle attached to a syringe is inserted into the fatty
tumour and some of the contents removed. The contents are spread onto a microscope slide and examined for the presence of cancer cell.
Cysts
Cysts are common non-cancerous tumours that can occur anywhere on or in a dog's body. Sebaceous cysts are benign
tumours that can reach an inch in size. Sebaceous cysts are filled with dead skin cells and sebum (oil) that produces the cheesy substance seen when the cyst is ruptured, either surgically or accidentally.
While usually non-cancerous, cysts may require drainage or surgical removal to prevent infection.
Cocker Spaniels are especially prone to sebaceous cysts.
Histiocytomas
Histiocytomas are very red, dome-shaped growths that appear on the ears, face and feet of younger dogs, most often those under age two. The sudden development of histiocytomas can be alarming.
Histiocytomas are often painful to the touch, but not generally associated with cancer. The exact cause of histiocytomas is unknown, but a viral cause is suspected.
Most histiocytomas resolve on their own within three months, but because they can be itchy a topical steroid may be prescribed. If the growth is causing pain or intense scratching that doesn't resolve with topical steroids, surgical removal is warranted.
Histiocytomas are common in Boxers, Dachshunds, Labrador Retrievers and Staffordshire Terriers.
Perianal Gland Tumours
Perianal gland tumours, or perianal adenomas, are most common in un-neutered male dogs. Perianal gland
tumours occur in the cells of the oil glands at the base of the tail around the anus.
While most perianal gland tumours are non-cancerous (adenoma), a biopsy may be required to rule out a cancerous form of perianal gland
tumour (adenocarcinoma). Perianal gland tumours can cause pain or become infected—their location makes infection quite likely.
Because perianal adenomas are stimulated by the hormone testosterone, most veterinarians will recommend neutering the dog. The
tumour(s) may be removed at the time of neutering or at a later date. If the
tumours are small, they can often be "frozen" with liquid nitrogen.
Other Non-Cancerous Tumours
A number of other non-cancerous tumours affect dogs. These include:
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Warts are generally harmless. Warts can be caused by a papilloma virus or by an irritant. Warts caused by a papilloma virus can be contagious to other dogs and often affect younger dogs. Papilloma usually produces a large number of warts on the face, neck and/or limbs. Once all the warts resolve the dog is considered immune to the virus.
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Skin tags are benign growths that stick out from the skin, and which are sometimes described as looking like "bits of chewing gum" stuck to the skin. Skin tags generally occur in older dogs are usually only removed if they become irritated or bleed. A tick is often mistaken for a skin tag, especially if the tick has attached in an area not easily examined by the owner.
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A hematoma is a collection of blood under the skin caused by physical trauma. Hematomas usually resolve by themselves. Earflap hematomas occur when a dog vigorously shakes his head in response to ear infections or ear mites. A large earflap hematoma may require drainage.
Non-Cancerous Tumours or Malignant Growths?
While most non-cancerous tumours are safe, there is always the slim possibility that apparently benign
tumours will become malignant.
The best course of action is to have a veterinarian examine any growths on your dog's body and decide whether or not a biopsy is necessary. Like many things, when it comes to non-cancerous
tumours, being safe is much better than being sorry. |
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| Some Dogs Carry 'Contagious' Cancer |
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Medical anomaly poses no threat to humans, experts say
By Ed Edelson, HealthDay Reporter
THURSDAY, Aug. 10 (HealthDay News) -- Researchers are describing what seems to be a real-life medical nightmare: A cancer that spreads from animal to animal like an infection.
Luckily for humans, this malignancy occurs only in dogs, and there's no need for people to be worried about it, experts say.
"It's a scientific curiosity," said Robin Weiss, professor of viral oncology at University College London, and a member of the team reporting the discovery in the journal Cell. "There is no evidence of transfers of human cancers from one person to another, except in very special circumstances, so we should not say that a human cancer patient is dangerous to others."
The cancer, called canine transmissible venereal tumor (CTVT), was first isolated from 16 dogs in Italy, India and Kenya. In each case, a study of the tumors' genetic material showed that it differed from that of the dog in question -- suggesting that it had been passed from another dog.
Further study of cancers from 40 other dogs in five continents found that the tumors were almost genetically identical, meaning that they originally came from a single source and had somehow spread across the globe.
Working with geneticists and computer experts in Chicago, the researchers compared the genetic material of tumors to that of specific breeds of dogs. They concluded that the cancer most likely arose more than 250 years ago -- perhaps as long as 1,000 years ago -- in a wolf or Asian dog such as a Husky or Shih Tzu.
CTVT is transmitted primarily through sexual contact, but experts believe it can also be picked up as dogs lick, bite or sniff tumor-affected areas. It is seldom fatal and usually disappears in three to nine months, just long enough for the dog to pass it on.
"One aspect where this is related to human cancer is not in the mode of transmission, but what it tells us about the nature of cancer," Weiss said.
Generally, as cancers become more aggressive, they become less stable genetically, he said. But CTVT has had the same genetic makeup for centuries and is "the oldest tumor cell lineage known to science," which means that it has become genetically stable, Weiss said.
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"This questions the theory of instability," he said. "I don't think that instability is inevitable as a tumor gets worse and worse."
The report also raises wildlife conservation issues, added Elaine Ostrander, chief of the cancer genetics branch at the U.S. National Human Genome Research Institute, who wrote an accompanying commentary.
Similar cancers are known to exist in two other species, the Tasmanian devil and the Syrian hamster, Ostrander said. For these types of endangered species, exposure to CTVT might endanger the population's survival, she wrote.
There appears to be no danger to humans from the sort of cancers seen in these animals, Ostrander said. While CTVT may occur in stray dogs, pedigreed dogs are usually not allowed casual sex, and the cancer "can't be transmitted to humans by handling dogs," she said.
"We always wonder when we see something in the animal kingdom if we will see the same thing in humans," Ostrander said. "We don't see any human evidence in this case."
More information
There's more on the genetics of cancer at the U.S. National Cancer
Institute. |
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