TUMORS AND CANCER
Definitions
The mention of the words tumor or cancer cause most people to think of the death of their pet. Despite tremendous progress in the treatment of tumors, most people unfortunately still find their minds drawn into the worst thoughts possible. It is important to know that most tumors in domestic pets can be cured with the pet living normally for years after treatment.
It is first important to understand the language of this branch of medicine as many terms are used to describe abnormal growths in the body. The words neoplasia or neoplasm are the proper terms used to describe any new and abnormal growth in the body. These words do not describe how "dangerous" a growth may be, only that an abnormal growth does exist. The word tumor is sometimes used instead of the word neoplasm. More correctly, the word tumor describes a swelling of or in a tissue. Oncology is the study of neoplasia or tumors.
The word benign means not malignant, and that the chances for recovery are favorable. It may also be used to describe a neoplasm that is not likely to spread to other parts of the body. The word everyone dreads most is malignant. A malignant tumor is one likely to become worse with time, likely to spread locally or to distant parts of the body and likely to ultimately lead to death of the pet. These would be the most dangerous types of neoplasms. Cancer is the common term for a malignant neoplasm so this word is commonly used to indicate a severe type of tumor.
Some tumors are classified as pre-malignant meaning that the tumor may be benign now but is likely to become malignant if more time goes by. These tumors may be removed before they turn into a cancerous growth. Another term commonly used is metastasis. This means that a neoplasm has spread from the area or organ where it originated to grow (also) in another organ or area. Once a neoplasm has metastasized it becomes very difficult to treat and will cause more damage to the pet.
Causes of Neoplasia
Although our ability to diagnose and treat all types of tumors has come a long way in the last decades, we are still far from understanding what actually causes a particular tumor to form. Owners commonly ask, "what caused it?" when the diagnosis of neoplasia is discussed with the veterinarian. Unfortunately, most doctors are left to say that any such growth arose spontaneously, and that we just don't know, nor can we ever (yet) be exactly certain why.
It has been determined that radiation, poisons and toxins, viruses, hormones in the male or female, chronic irritations, internal and external parasites, and certain drugs can cause neoplasia. Most importantly, it seems that genetic factors are probably the single most important reason any individual will get a certain tumor. In other words, our dogs all have certain inherited genes, which either help to protect against the development of neoplasia or to some degree increase the chances that certain tumors will form. At best with good preventative care and by avoiding all the things mentioned above which are known to contribute to cancers and tumors, the odds of developing neoplasia can be kept as low as possible.
While tumors can occur at any age, they are most common in dogs and cats older than 5 years of age. Some tumors are more common in certain breeds (genetics again) and in pets with certain coat colors. Overall the chances any given animal will get any type of tumor are only about 4 out of every 1000! Of this rate, only about 35-45% of these pets will have malignant tumors, again supporting the fact that most tumors are curable. Boxers and Cocker Spaniels seem to have a slightly higher rate of tumors; the Beagle and mixed-breed dogs seem to have a lower rate. Skin tumors are the most common type of neoplasia in the dog, oral/digestive tumors more common in cats. Cats with feline leukemia virus have a much higher rate of cancer.
Diagnosis of Tumors and Cancer
In all other sections within this program, diseases are indicated based on clinical signs or symptoms that will usually appear. As neoplastic growths can occur in any tissue or organ, in any part thereof, and even spread to multiple areas, it is impossible to say that any one or general set of clinical signs points to some type of tumor. An important point to remember at all times when discussing neoplasia; tumors do not follow exact or specific patterns, they have tendencies, but we can only predict in general terms what a tumor will do once it begins to grow inside the dog.
External tumors will be the most obvious, appearing as a swelling, sore or evidently irregular growth. Some external growths may ulcerate, discharge or even begin to decay. Signs of internal tumors are often vague and can include pain, gain or loss of appetite, gain or loss of weight, swelling to the abdomen or feet, unusual bleeding, weakness, trouble breathing, constipation or diarrhea, vomiting, changes in gum color, seizures, paralysis, changes in thirst or urinary habits, fever, and a few other symptoms we have probably overlooked. With this said, one can see that the diagnosis is often less than obvious.
A veterinarian will use most any of the commonly used tests to help determine if a tumor is present. These include blood analysis, urinalysis, X-rays, ultrasound, cytology and biopsy. Where possible, cytology is an excellent preliminary test for neoplasia. Part of suspected tumors can often be aspirated into a syringe, washed off of an internal surface or scraped free from an area and placed on a slide to be stained and examined by the veterinarian under the microscope. While this may not constitute an exact diagnosis, it is easy and inexpensive and will quickly help the veterinarian determine what should be done to best help the pet.
A biopsy, however, is the only sure and accurate way to determine exactly what type of tumor is present and if it is benign or malignant. A biopsy is performed by taking a small section from a suspected tumor and having a veterinary pathologist examine it for an exact determination. A biopsy may be taken before surgery to help the doctor know what he/she is dealing with and how to best attempt a cure, or after all of a mass is removed to find out what is being treated and if more surgery or other therapy will be necessary.
TREATMENT OF TUMORS AND CANCER
Just as it is nearly impossible to list exact symptoms for the all the various types of tumors that can exist, is difficult to say precisely what treatment(s) or therapy will work best. The most common and most effective type of tumor therapy used on dogs and cats is surgery. Up to 80% of all tumors can be completely removed and cured with surgery.
Chemotherapy is also available and many cities now have specialists who have the drugs and expertise to provide pets with the most up-to-date therapy available. Chemotherapy is often the only reasonable coarse for pets with widespread tumors and cancers of the blood or lymphatic systems.
Other types of therapy include cryotherapy or the freezing of tumors, radiation therapy which is available only in limited areas, immunotherapy which employs the use of antibodies and other immune system components to fight tumors, radiosurgery which employs electricity to cut and destroy tumor tissues, and various combinations of all the aforementioned methods. The best treatment will depend on the techniques available, the general health of the patient, the cost involved, the type of neoplasia present and if and where it may have spread, and the skills of the doctors treating the patient.
Common General Tumor Types and Terms
Adenoma: benign tumor from glandular surface lining tissues.
Adenocarcinoma: malignant growth from glandular tissues.
Carcinoma: malignant tumor from surface lining tissues.
Cyst: benign growth, non-neoplastic and filled with fluid or semi-solid material.
Mass: general term for any lump or growth, may not imply neoplasia.
Polyp: any abnormal protrusion from a mucus membrane. (gums, rectum, etc.)
Sarcoma: tumors from supportive tissues such as blood, bone and muscle.