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What is Canine Cancer?

Cancer is a group of diseases characterized by the uncontrolled growth and spread of abnormal cells. The most obvious symptoms of cancer in dogs are tumors, smooth or bumpy, which can appear anywhere on the body and can be seen or felt, but a wide range of symptoms are possible, depending on the type of cancer. According to the American Cancer Society, cancer is a group of diseases characterized by uncontrolled growth and spread of abnormal cells. If the spread is not controlled, cancer can result in death.

How Does Longlife Treat Canine Cancer?

A cancerous tumor feeds off vital nutrients that flow through the bloodstream. Researchers have found that shark cartilage stops blood vessels from feeding and growing within the tumor. In clinical studies on the use of shark cartilage supplements, it was found that tumors did not grow larger than 2 millimeters in size, due to an antiangiogenesis effect, or a prohibiting of the growth of new blood vessels inside the tumor.

Longlife for Dogs is made from 100% pure shark cartilage and is formulated to promote maximum absorption. Longlife is a helpful tool in the prevention of metastasis during or after chemotherapy and can be combined with chemotherapy to increase appetite and help protect the immune system. Longlife for Dogs should be used as supportive supplements, not a substitute for quality care from a trusted veterinarian or oncologist.

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Characteristics of Cancer in Dogs

Abnormality: Cells are the structural units of all living things. Each of us has trillions upon trillions of cells, as does a growing tree, a sponge in the ocean, or a dog asleep by the fire. Cells make it possible for us, and for dogs, to carry out all kinds of functions of life: breathing, walking, jumping, digesting food, and so on. However, all of these functions can only be carried out by normal healthy cells. Cancerous cells stop functioning as they should, become useless to the body, or become hostile to the body’s purpose.

Uncontrollability: The most fundamental characteristic of cells is their ability to reproduce by dividing: one cell becomes two, two become four, and so on. In most parts of the body, cells continually divide and form new cells to supply the material for growth or to replace worn-out or injured cells. When a person cuts his or her skin, certain cells leap into action, dividing and dividing, producing news cells until the tissue is healed and the skin is repaired. (Afterwards, they return to their normal rate of division.) In contrast, cancer cells divide in a haphazard manner that does nothing good, and often something bad, for the body. These typically pile up into a nonstructured mass. This mass is known as a tumor.

Invasiveness: Sometimes tumors do not stay harmlessly in one place. Tumors often destroy the part of the body in which they originate and then spread to other parts, where they cause new harm. This is what differentiates malignant growths from benign growths, which remain in the part of the body in which they start. Although benign tumors may grow quite large and press on neighboring structures, they do not spread to other parts of the body. Frequently, they are completely enclosed in a protective capsule of tissue, and they typically do not pose danger to life. Malignant tumors do spread, and are life threatening.

Many diseases: Although cancer is often referred to as a single condition, it is actually comprised of dozens of different diseases. These diseases are characterized by site of origin, method and speed of growth, and character of the abnormal cells. Cancer can arise in many sites and behave differently depending on its point of origin. It is important to understand that cancer originating in one body organ takes its characteristics with it even if it spreads to another part of the body. For example, metastatic lung cancer starts in the lung; even if it spreads to other parts of an organism’s body, it retains the characteristics of its original organ.

In a dog, this abnormal cell phenomenon is called, simply, Canine Cancer. Canine cancer is a common disease which requires prompt and decisive veterinary attention. Dogs with cancer elicit a strong emotional (and, it must be said, economic) toil on the animal’s caretakers. Huge strides are being taken to help veterinarians recognize cancer in dogs and to assist in control and cure. Advances in human cancer diagnosis and treatment often mirror the same protocols veterinarians utilize to diagnose, control, and treat cancer in animals.

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Canine Cancer Definitions of Terminology

To best understand cancer, it is helpful to understand a few terms:

Cancer: Any malignant, cellular tumor; cancers are divided into two broad categories of Carcinoma and sarcomas: A carcinoma is a malignant growth made up of epithelial cells (which form a membrane over an organ) tending to infiltrate surrounding tissues and give rise to metastases. A sarcoma is a malignant tumor originating from connective tissue or blood or lymphatic tissues.

Neoplasm: an abnormal new growth of tissue in animals or plants; a tumor.

Benign tumor: One lacking the properties of invasion and metastasis and showing a lesser degree of abnormal cellularity than malignant tumors. These are usually surrounded by a fibrous capsule.

Malignant tumor: Has the properties of invasion and metastasis and displays cells with widely varying characteristics.

Metastasize: to spread throughout the body, of cancer cells.

Growth: any kind of an abnormal increase in size of tissue.

Lump: A growth or fluid-filled cyst or any structure rising above the normal surface of a tissue plane.

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Hemangiosarcoma in Dogs

Hemangiosarcoma is an aggressive cancer that arises from the blood vessels. The cancer can occur anywhere in the body, but there are several locations that are more common. Early and aggressive treatment can lengthen the dog's life, but this cancer is often metastatic and complete remission is rare.

Dogs At Risk for Hemangiosarcoma

Hemangiosarcomas can occur in any dog. It does not discriminate on the basis of breed, age, or sex. However, several breeds of dogs seem to be at greater risk for hemangiosarcoma, including German Shepherds, Golden Retrievers, Boxers, and English Setters.

Researchers do not currently understand why dogs develop hemangiosarcoma. Because of the increased incidence in several breeds, a genetic link appears to be one of several likely causes. Because hemangiosarcoma is rarely found in humans, less research has been done and the amount of information about the cause of this tumor is somewhat limited.

Symptoms of Hemangiosarcoma

Hemangiosarcomas can occur anywhere on or in a dog's body, but primarily are present in the spleen, liver, heart, and skin. The skin form of hemangiosarcoma has a better prognosis and recovery rate than the internal forms. The skin form is more present in cats, and is sometimes associated with sun damage on light-skinned/haired animals. The internal form is usually diagnosed by the palpitation of a large mass in the abdomen or with symptoms of sudden blood loss, which results from the rupture of the fragile tumor and a subsequent loss of blood into the abdomen. Symptoms include weakness or collapse and pale mucous membranes. Occasionally, dogs will have symptoms of chronic blood loss, which include pale gums, slow capillary refill time (CRT), irregular heart rate, and generalized weakness.

Hemangiosarcoma Diagnosis

Once a tumor is suspected, abdominal and chest X-rays are often performed to determine the extent of organ involvement and to find out whether or not metastasis is present. Hemangiosarcoma is an aggressive tumor, and metastases are often present at the time of initial diagnosis. A biopsy or positive identification of a removed tumor by a veterinary pathologist is usually recommended.

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Lymphoma in Dogs

Lymphoma, otherwise known as Lymphosarcoma, is a common cancer and can occur in the lymph nodes, spleen, liver, and other organs. The cancer can be aggressive and if left untreated can be fatal.

Dogs at Risk of Lymphoma

Lymphomas primarily affect middle-aged to older dogs. There does not appear to be a differentiation as to breed or sex. Only a small portion of dogs are clinically ill at presentation; the majority are brought in because of recently identified swellings or lumps.

Causes of Lymphoma

While we understand how lymphomas form, we still do not understand why. In cats, there appears to be a strong link between some forms of lymphoma and infection with feline leukemia virus, but in dogs such a link is not apparent. Some authors have speculated that environmental factors (exposure to pesticides or strong magnetic fields) might play a factor, but there is currently no strong proof of this. At the same time, some studies have also hinted at a possible genetic correlation.

Symptoms of Canine Lymphoma

The symptoms of lymphoma are related to the location of the tumor(s). Tumors that develop in the lymph nodes often present as swellings with no other symptoms. The gastrointestinal form often is accompanied by vomiting, diarrhea, weight loss, and lack of appetite. The chest form often presents with shortness of breath and muffled heart sounds. The cutaneous (skin) form can present in several different ways, including single or multiple lumps in the skin or mouth. These bumps can itch or be red and ulcerated.

Diagnosis of Canine Lymphoma

Lymphoma is diagnosed with a combination of tests, including blood tests, fine needle of the tumor, biopsies, X-rays, and ultrasound. The exact tests performed depend on the location of the tumor.

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Histiocytomas in Dogs

Histiocytomas can affect dogs of any age or breed. Though they can appear on any location on the body, the vast majority of histiocytomas appear on the head. Histiocytomas usually occur on dogs under three years of age; they are one of the most common tumors in this age group.

These tumors appear rapidly and are small, round, and hairless. They will often ulcerate and then become smaller and go away. They usually appear as a solitary mass, but more than one may be present at a time. These tumors are benign and are not considered to be a health risk.

Treatment for Histiocytomas

Treatment often involves simply letting the tumor run its course. Histiocytomas can be surgically removed, if they are bothering the dog and are in a location where removal will allow for closure of the skin. They can also be treated with topical steroids and antibiotics if they ulcerate or become inflamed or infected. However, most dogs never receive nor require any treatment intervention. If a dog owner sees a small tumor that develops on his or her dog, he or she should make sure to have it examined by a veterinarian.

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Mammary Tumors in Dogs

Mammary tumors are the most common tumors in female dogs that have not been spayed. Mammary tumors can vary from small, simple nodules to large, aggressive, metastatic growths. With early detection and prompt treatment, even some of the more serious tumors can be successfully treated. Cats also suffer from mammary tumors, and they have their own unique set of problems that will be discussed in a separate article.

Dogs At Risk of Developing Mammary Tumors

Mammary tumors are more common in unspayed, middle-aged female dogs (those between 5 and 10 years of age), although they can, on rare occasions, be found in dogs as young as 2 years. (They are rare in dogs that were spayed at less than 2 years of age.) Occasionally, mammary tumors will develop in male dogs (in the same way that men can sometimes develop breast cancer), and these are usually very aggressive and have a poor prognosis.

Spaying greatly reduces the chances of a female dog developing this condition. In those females spayed prior to their first heat cycle, mammary tumors are extremely rare. The risk of malignant mammary tumors in dogs spayed prior to their first heat is 0.05%. It is 8% for dogs spayed after one heat, and 26% in dogs spayed after their second heat. The elimination or reduction of certain hormones causes the lowering of incidence of the disease in dogs that have been spayed—this is the scientific consensus. These hormones are probably estrogen, progesterone, a similar hormone, or possibly a combination of two or more of these.

Types of Canine Mammary Tumors

There are multiple types of mammary tumors in dogs. Approximately one-half of all mammary tumors in dogs are benign, and half are malignant. All mammary tumors should be identified through a biopsy and histopathology (microscopic examination of the tissue) to help in the treatment of that particular type of tumor. This is, of course, a role for the veterinarian.

The most common benign form of canine mammary tumors is actually a mixture of several different types of cells. Single tumors rarely possess more than one type of cancerous cells. This combination cancer in the dog is called a “benign mixed mammary tumor” and contains glandular and connective tissue. Other benign tumors include complex adenomas, fibroadenomas, duct papillomas, and simple adenomas.

The malignant mammary tumors include the following: tubular adenocarcinomas, papillary adenocarcinomas, papillary cystic adenocarcinomas, solid carcinomas, anaplastic carcinomas, osteosarcomas, fibrosarcomas, and malignant mixed tumors.

Canine Mammary Tumor Symptoms

Mammary tumors present as a solid mass or as multiple swellings. When tumors do arise in the mammary tissue, they are usually easy to detect by gently touching and retouching the mammary glands. When tumors first appear they will feel like small pieces of pea gravel just under the skin. They are very hard and are difficult to move around under the skin. They can grow rapidly in a short period of time, doubling their size every month or so.

The dog normally has five mammary glands, each with its own nipple, on both the right and left side of its lower abdomen. In half of the cases, more than one growth is observed. Benign growths are often smooth, small, and slow growing. Signs of malignant tumors include rapid growth, irregular shape, firm attachment to the skin or underlying tissue, bleeding, and ulceration. Occasionally tumors that have been small for a long period of time may suddenly grow quickly and aggressively, but this is the exception and not the rule.

It is very difficult to determine the type of tumor based on physical inspection. A biopsy or tumor removal and analysis are almost always needed to determine whether the tumor is benign or malignant, and to identify what type it is. Tumors, which are more aggressive, may metastasize and spread to the surrounding lymph nodes or to the lungs. A chest X-ray and physical inspection of the lymph nodes often help in confirming this.

Mammary cancer spreads to the rest of the body through the release of individual cancer cells from the various tumors into the lymphatics. The lymphatic system includes special vessels and lymph nodes. There are regional lymph nodes on both the right and left sides of the body under the front and rear legs. They are called the "axillary" and "inguinal" lymph nodes, respectively.

Prevention of Mammary Tumors in Dogs

Few cancers are as easily prevented as mammary cancer in dogs. There is a direct and well-documented link between the early spaying of female dogs and the reduction in risk of mammary cancer. Dogs spayed before their first heat have an extremely small chance of ever developing mammary cancer. Dogs spayed after their first heat but before 2.5 years are at greater risk, but face less risk than dogs that were never spayed or spayed later in life. Early spaying is still one of the best things pet owners can do to improve the health of their dogs.

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Testicular Tumors in Dogs

Testicular tumors are considered one of the most common tumors in older intact (unneutered) male dogs. The overall incidence in dogs is not very high because of the large number of dogs that are castrated. However, in intact male dogs, these tumors are considered fairly common. The tumors are usually fairly easy to recognize and diagnose. Treatment is castration; this is usually sufficient to eliminate the disease.

Dogs At Risk of Testicular Tumors

Testicular tumors are most common in intact (unneutered) older male dogs. However, they can occur in intact males of any age. There does not appear to be any breed predilection for this tumor, and the cause of testicular tumors is unknown. Dogs that have one or both testicles that are not descended (cryptorchid) are 13 times more likely to develop a tumor in the undescended testicle than dogs with normal testicles. Except for the increased risk of these tumors in cryptorchid dogs, no other risk factors are readily apparent.

Types of Canine Testicular Tumors

There are three common types of testicular tumors: Sertoli cell tumors, seminomas, and interstitial cell tumors. While there are differences in the types of tumors, they are often treated similarly and are therefore commonly lumped together as testicular tumors.

Symptoms of Testicular Tumors in Dogs

Sertoli cell tumors show symptoms of swelling of the testicular and scrotal area. Approximately half of Sertoli cell tumors produce estrogen. In that case, the dog suffers symptoms of hyperestrogenism. The symptoms include an enlarged prostate gland, enlarged mammary glands and nipples, symmetrical hair loss, anemia, and the tendency to attract other male dogs. Sertoli cell tumors may metastasize to the abdomen, lung, thymus, and brain; however, this occurs in less than a quarter of cases.

Diagnosis of Canine Testicular Tumors

Based on history, presentation, and most of all pathological identification through a biopsy or microscopic examination of the removed tumor. Dogs suspected of a testicular tumor should also have abdominal and chest X-rays to check for metastasis as well as a chemistry panel and a blood count.

Prognosis for Dogs with Testicular Tumors

For dogs with treated testicular cancer, the prognosis is usually very good. The low rate of metastasis makes surgical castration very successful and curative in most dogs. Dogs that develop hyperestrogenism from Sertoli cell tumors often have a regression of symptoms once the tumor has been removed. In severe hyperestrogenism that results in anemia, some animals may need transfusions and more aggressive treatment. The prognosis for testicular tumors that have metastasized is more guarded and the outcome varies widely depending on location, type, and treatment.

Prevention of Canine Testicular Tumors

Testicular tumors are easily prevented through routine castration of male dogs. Castration in young dogs prevents aggression, roaming, urine marking, and a variety of other unsavory male behaviors. Castration is safe and relatively inexpensive, and in the long run saves the owner money.

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Mast Cell Tumors in Dogs

Canine mast cell tumors account for up to 20% of all skin tumors in dogs. While they often appear small and somewhat insignificant, they can be a very serious form of cancer. Some mast cell tumors are easily removed without the development of any further problems, while others can lead to a life-threatening disease. Proper identification and treatment are very important in controlling these tumors.

Canine Mast Cell Tumors Defined

Mast cells are cells that normally occur in the skin and other tissues, such as the intestines and respiratory tract. They are part of the immune system of the body. They contain large amounts of histamine, heparin, and proteolytic enzymes (enzymes which break down protein). These can be toxic to foreign invaders, such as parasites, and are released when the mast cell is triggered by the immune system.

A mast cell tumor is formed from many of these mast cells. Because of the histamine, heparin, and enzymes present in mast cell tumors, they can create problems when damaged or removed. Large amounts of these substances can be released into the body and have significant effects on heart rate, blood pressure, and other body functions. Sites where the tumors are removed can sometimes refuse to heal and can become difficult to manage.

Dogs At Risk of Developing Mast Cell Tumors

Mast cell tumors can develop in all ages and breeds of dogs. There appears to be a hereditary factor to these tumors most common in Boxers, Boston Terriers, Pugs, English Bulldogs, and other brachiocephalic breeds (those having a short, wide head). Golden Retrievers may also be at increased risk. Most mast cell tumors develop in older dogs, usually those 8.5–9.5 years of age.

The exact cause of mast cell tumors is still unknown. A viral source has been suggested, as well as hereditary and environmental factors. It is quite possible that there are a variety of causes for the development of this tumor. Because this tumor is not found in humans, less research and information has been available for the veterinarian than for tumors that are found in both humans and animals.

Symptoms of Mast Cell Tumors in Dogs

The appearance of mast cell tumors can be widely variable. They can be either benign or malignant and can be found on any part of the body. They are found most commonly on the trunk, limbs, and perineal (genital) area, and can be found on the skin or in the underlying tissue. They can be single or multiple and can be smooth, bumpy, or even ulcerated.

Systemic signs, such as vomiting, duodenal ulcers, blood in the stool, and abnormalities in blood clotting, occur in some dogs with mast cell tumors. These signs result from the release of histamines from the active mast cell tumors.

Diagnosis of Mast Cell Tumors in Canines

Since they occur in a variety of shapes and locations, a biopsy is necessary to properly identify a mast cell tumor.

Mast cell tumors are commonly graded and staged (classified) as to how they are expected to behave. This is performed by examining the tumor after it has been removed. The grading and staging helps determine what type of further treatment may be necessary and the prognosis.

Mast cell tumors are "graded" as to how likely they are to be malignant. The higher the grade, the more serious the tumor.

  • Grade I: Occur in the skin and are considered benign. Although they may be large and difficult to remove, they tend not to spread to other areas of the body. Most mast cell tumors are Grade I.
  • Grade II: Extend below the skin into the subcutaneous tissues. Their cells show some characteristics of malignancy and their response to treatment can be unpredictable.
  • Grade III: Invade areas deep below the skin, are very aggressive, and require more involved treatment.

In addition to grading mast cell tumors, they are also staged, which is a measurement of how they have spread in the body. A tumor is staged after it is removed and examined, along with the neighboring lymph nodes. Staging is based on how many tumors were present, how involved the lymph node is, and whether the entire tumor was removed.

  • Stage 0: One tumor in the skin incompletely removed, with no lymph node involvement.
  • Stage I: One tumor in the skin, with no lymph node involvement.
  • Stage II: One tumor in the skin, with lymph node involvement.
  • Stage III: Multiple large, deep skin tumors, with or without lymph node involvement.
  • Stage IV: One or more tumors with metastasis in the skin, with lymph node involvement. This stage is subdivided into those that have no other signs (substage a) and those that do have some other clinical signs (substage b).

Prognosis of Mast Cell Tumors in Dogs

The prognosis depends primarily upon the grade and stage of the tumor. The lower the grade, the better the prognosis. In addition, dogs with Stage I tumors have the best prognosis, compared to those staged higher. Dogs with tumors on the limbs appear to have the best prognosis, much better than those with tumors in the nail bed, genital areas, muzzle, and mouth. Finally, those dogs with mast cell tumors in the internal organs have the least favorable prognosis.

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Bone Cancer in Dogs

Bone cancer in dogs can be a challenging disorder to overcome. Bone cancer can occur in any canine. The hallmark of bone cancer (as with all cancers) is uncontrolled cell growth, invasion of cells into nearby structures, and sometimes a dispersal to distant organs, which is termed metastatic cancer. Since any cell in the dog's body has the potential to develop into a cancerous cell, bone cancer dramatically illustrates what can happen when illness occurs.

When a cell turns cancerous by a disruption of its own physiology, normal neighboring cells usually consume the rogue cell. On other occasions, the defective cell simply self-destructs and is swept away. But in certain circumstances, a modified cell (mutant) makes more cells just like itself. More and more cells arising from that single mutated cell eventually change the environment and carve out their own territory, spreading themselves into more and more neighborhoods. Metastatic bone cancer cells break away and flow to entirely new environments within the dog's body and begin the malignant process all over again.

Cancer is also termed neoplasia, which means new growth. A cancerous cell grows faster than normal and divides and multiplies at an abnormal rate; its offspring do likewise. From that one abnormal neoplastic cell, more of its kind invade and crowd out surrounding tissues. With bone cancer, there are four types of cell lines capable of evolving into a neoplastic condition:

Osteosarcoma: causing nearly 80% of all bone cancers, this most common form of bone cancer arises from cells that deposit bony minerals. Aggressive invasion and rapid growth make this form of cancer a dreaded threat.

Chondrosarcomas: these tumors arise from the cartilage joint surfaces at the ends of bone and generally have a less aggressive tendency to invade and spread than osteosarcomas.

Fibrosarcomas: originate from fibrous connective tissue adjacent to bone, are locally invasive into the bone, and have a low tendency to spread.

Synovial cell carcinomas: originate from joint tissues and invade the associated bone. These tumors are less aggressive than osteosarcomas.

A definitive diagnosis of bone cancer can only be made via microscopic evaluation of a bone biopsy. Veterinary pathologists classify the degree of malignancy of the cells and likeliness of metastasis to other tissues. Neoplastic cells can be carried by the blood and lymph from the original site of the cancer to distant tissues, at which time a new cancerous growth arises. Called metastatic cancer, whenever distant growths are present in a dog's body, the magnitude of the ill effects on the patient are remarkably increased, and the chances of a cure drastically reduced.

At-Risk Breeds for Canine Bone Cancer

Most commonly seen in long bones such as the femur, bone cancer has a predilection for larger breeds, including the Greyhound, Saint Bernard, and Mastiff.

Diagnosis of Canine Bone Cancer

Chronic, low-grade lameness with gradually increasing swelling near a joint alerts the veterinarian to the potential of a tumor. Radiographs of the affected area will display changes in a bone that are totally unlike the defects usually associated with arthritis. On occasion, an apparently normal dog will be presented with a spontaneous lameness. A physical examination, followed by a radiographic evaluation, will reveal the cause of the break to be due to bone cancer. This break is termed a pathological fracture.

Osteosarcoma continues to be one of the most challenging types of cancer to treat. Part of the therapeutic challenge arises from the fact that at the time of diagnosis there often has already been metastasis to other areas of the body.

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