Neoplasia, Tumors and Cancer
Neoplasia describes a process involved in several different diseases. It is therefore difficult to give an all-encompassing definition. However, it is generally recognized that neoplasia is the uncontrolled, abnormal growth of cells or tissues in the body, prior to a lump or abnormal growth developing. Once developed, the abnormal growth is called a neoplasm or tumor. Tumors can be benign or malignant. Benign and malignant tumours A benign tumor is a mass of cells that lacks the ability to invade neighboring tissue or spread throughout the body. Benign tumors typically have an outer fibrous sheath of connective tissue and grow more slowly than malignant tumors. Malignant tumors usually grow more aggressively, they invade the tissues surrounding them and can metastasize (spread throughout the body). The actual swelling or appearance of a neoplasm is often described as a “tumor” or “mass”. The word “cancer” is often used instead of neoplasia, but only malignant neoplasms are true cancers.
INCIDENCE OF NEOPLASIA AND CANCER
Neoplasia is common in pets and the incidence increases with age.
Approximately 32% of all cats over 10 years of age will die from some type of cancer. Most feline cancers occur in cats 10 to 15 years of age – although lymphoma is an exception as this occurs most often in young cats. Cats commonly develop skin tumors; 25% of all feline cancers are skin cancers, with 50% to 65% of them being malignant. The next most common type of feline cancer is breast cancer (17%) and approximately 10% of all feline tumors are found in the mouth.
It has been estimated that almost 50% of deaths in dogs over 10 years of age are cancer-related and approximately 25% of all dogs will die from cancer. Overall, the incidence of cancer is 3 times greater in female dogs compared to males. This difference is due to the much high rate of mammary cancer in bitches. The incidence of cancer in pure-bred dogs is substantially higher. For example, one in five Golden Retrievers is diagnosed with hemangiosarcoma and is likely to die from it. Other breeds in which cancer is more common include the Boxer, Bernese Mountain dogs and Greyhound.
Physical examination and a pet’s medical history may lead a veterinarian to suspect neoplasia. Additional tests, such as x-rays, ultrasound examination and blood-tests may be necessary to confirm the diagnosis. In some cases, taking a tissue sample (biopsy) from the neoplasm for microscopic examination may also be necessary. This examination can help determine whether the neoplasm is benign or malignant. Additional tissue samples from other organs such as the lymph nodes may be necessary to determine the rate and extent of spread of a malignant neoplasm.
Common signs of neoplasia in small animals include
• Abnormal swellings that persist or continue to grow
• Sores that do not heal
• Weight loss
• Appetite loss
• Reluctance to exercise or a loss of stamina
• Persistent lameness or stiffness
• Offensive odor
• Difficulty eating or swallowing
• Difficulty breathing, urinating, or defecation
• Bleeding or discharge from any body orifice
• Excessive drooling
It is worth remembering that in cats, 52% of cancers occur in body areas that can easily be examined (skin, mammary glands, mouth). Frequent examinations by the pet owner can lead to early detection.
The causes of most neoplastic diseases are not known. Prevention is therefore difficult and early detection is the best way to manage neoplasia.. Cancer is a “multi-factorial” disease. This means it has no known single cause. Hereditary and environmental factors have been identified as risk factors contributing to the development of cancer in pets.
COMMON TYPES OF NEOPLASIA IN PETS
Skin neoplasia is common in older dogs, although developing tumors are usually benign. Cats also develop skin neoplasms, most of which are malignant. If you find a lump on your pet, your veterinarian should be consulted to determine whether it is malignant.
Mammary Gland (Breast)
Both cats and dogs can develop mammary neoplasms. In dogs, mammary cancer is the most frequently diagnosed cancer, accounting for 70% of all cancer cases. In dogs, 50% of all breast neoplasms are malignant, whereas in cats, more than 85% of breast neoplasms are malignant. Spaying your female pet before she is 12 months old will greatly reduce the risk of this type of neoplasia.
Head and Neck
Neoplasia of the mouth is common in dogs but less common in cats. Symptoms include tumors on the gums, bleeding, bad breath, or difficulty in eating. Because many swellings in these areas are malignant, early, aggressive treatment is essential. Neoplasms may also develop inside the nose. These can cause bleeding from the nose, breathing difficulty, or facial swelling. These symptoms should be checked by your veterinarian.
Lymphoma is a common form of neoplasia in dogs and cats, characterized by swelling of one or several lymph nodes in the body. In cats, one cause of lymphoma can be the contagious feline leukemia virus.
Testicular neoplasia is rare in cats. It is more common in dogs, especially those with retained testicles, i.e. testicles that did not descend correctly during maturation and may remain located in the abdomen or between the abdomen and scrotum.
Neoplasms inside the abdomen are common. Because of their location, they can be difficult to detect and an early diagnosis is unlikely. Symptoms of abdominal neoplasisa are weight loss or abdominal swelling.
Bone neoplasms are seen most often in large-breed dogs or dogs older than 7 years; they are rarely seen in cats. The most common sites are the leg bones, near the joints. Symptoms include persistent pain, lameness, and swelling in the affected area.
Many symptoms of neoplasia are also seen in non-neoplastic conditions, however, they still need prompt attention by a veterinarian for diagnosis. Neoplasia is often treatable; early detection and diagnosis will assist in getting the best possible treatment.
The various types of neoplasia require different individual treatment. This may include one, or a combination, of therapies such as surgery, chemotherapy, immunotherapy, radiation, hyperthermia (heating) or cryosurgery (freezing). Your pet’s overall health is, of course, important. Veterinarians may recommend dietary changes or other alterations to your pet’s life to help your pet respond better to the proposed treatment. Discuss with your veterinarian, the best treatment options for your pet and especially the risks and side-effects associated with these options Pain management is an extremely important aspect of treatment. In some cases, depending on the recommended course of treatment, your veterinarian may refer you to a cancer specialist, or speciality clinic. Some types of neoplasia can be cured, but other types can only be managed to decrease their spread to other organs and tissues of the body. This will prolong your pet’s comfort and quality of life as much as possible. Early detection of a neoplasm and the type of neoplasm are often the greatest factors which determine the success of treatment.
Depending on the severity, development and type of cancer, euthanasia may be considered. Before making your decision for treatment or euthanasia, discuss with your veterinarian the options available so that you can make the best choice for your pet and your family.
The success rate of any treatment is highly dependent on the type and severity of the neoplasia, as well as the aggressiveness of any treatment being undertaken. Benign neoplasms are usually easier to treat. Although some neoplasms, especially the more aggressive cancers, cannot be cured, treatment can both prolong and improve your pet’s quality of life.
Research means we are learning more and more about neoplasia. Animals today have a considerably better chance of being successfully treated for neoplasia and cancer than they did just a few years ago. New diagnostic methods, such as improved imaging techniques, can help detect neoplasia earlier. These will improve your pet’s chances of an early diagnosis and receiving early treatment. New treatments are being developed which will provide better success rates with less risk of side-effects.