Just like humans, animals can get all sorts of tumors. Almost any tissue in the body can be affected. But how and why do tumors start? And is a tumor the same as cancer?
Tumors are new growths of body tissue, known as neoplasms, which arise from a dysregulation of cell growth. They can occur in almost all body tissues. Various causes lead to either a change in the genetic material in a cell or an error in reading the genetic material during cell division. This results in cells that differ from the original cells of an organ: they exhibit altered behavior in terms of growth, aging, and death. In addition, they can leave their original location in the body via the blood and lymph vessels, settle in other tissues, and continue to grow there.
Degenerated cells arise daily in every living being. They are destroyed and broken down by a functioning immune system. If this does not happen to a sufficient extent, these cells can continue to divide and multiply, causing a tumor to grow.
Tumors can be divided into three classes according to their growth behavior:
Almost all tumors end in "-om" in their name. "Carcinoma" and "sarcoma" are always malignant tumors.
The causes of tumor diseases are diverse and continue to be researched scientifically. One of the main risk factors for both animals and humans is age. With increasing age, the risk of damage to the genetic material of cells also increases.
Some animal breeds are genetically more susceptible to certain types of tumors. However, some tumor diseases are also passed on to offspring regardless of breed.
Being overweight promotes the development and growth of tumors. Visceral fat, which surrounds the internal organs in the abdominal cavity, produces many pro-inflammatory messenger substances. This leads to chronic inflammation, which promotes tumor diseases. Fat cells also produce the sex hormone estrogen, which promotes the growth of tumor cells. Obese animals also produce more insulin than normal-weight animals. Insulin is also a growth factor for many tumor cells.
Other causes include:
Some tumors can remain completely symptom-free and undetected. Others can lead to malfunctioning of individual organs, impairment of the entire organism, and even death.
The general symptoms of a tumor disease are nonspecific. These can include:
Depending on the organ system affected, the following symptoms may occur:
After a general examination with palpation (manual examination of body parts), there are various imaging techniques available to visualize tumors. In addition to X-ray examinations, ultrasound, magnetic resonance imaging, and computed tomography (see corresponding articles) are primarily used for tumor diagnosis in animals. Using ultrasound, your veterinarian can assess the blood vessels of the tumor and their blood flow with the help of the Doppler method. The search for metastases is also carried out using X-ray and ultrasound examinations. Magnetic resonance imaging or computed tomography is used, for example, to diagnose tumors in the brain, bones, spinal canal, or pelvis.
When planning treatment and making a prognosis for a tumor, it is important to know what type of cell it is, whether the tumor is benign or malignant, how far it has spread, and how it behaves biologically. To do this, your veterinarian will take a sample of the tumor tissue. This is done via a biopsy or fine needle aspiration. A small amount of tissue is sucked out through a cannula using negative pressure. This allows deeper tissues and the lymph nodes that supply the tumor area to be reached. For both techniques, your animal will usually be put under a short anesthesia.
The sample material is examined in a pathohistological laboratory. There, a so-called staging (assessment of the tumor stage) and grading (assessment of the tumor grade) is performed.
Staging refers to the size of the tumor and whether and how much the tumor cells have already spread in the body. It is usually based on the TNM classification:
T = size of the primary tumor:
N = Lymph node involvement:
M = Metastases:
Grading is used to classify the degree of deviation of the tumor cells from the normal tissue of the organ. The higher the grade, the more malignant the tumor. Grading is determined separately for each type of tumor. In addition, due to the sometimes considerable differences between animal species, there are species-specific grading systems for some tumors. A general distinction is made between:
A variety of general blood values provide your veterinarian with further clues. In addition, specific tumor markers can be determined in the blood for some tumors. Tumor markers are components or metabolic products of tumor cells. However, the tumor markers developed for veterinary medicine to date are not specific to tumor disease, but also to other conditions, such as inflammatory organ diseases. If the results are positive, further tests must therefore be carried out.
In order to achieve the best possible treatment, there are various treatment options that can be carried out in different sequences and also combined. Your veterinary practice will advise you individually on what is appropriate for the stage and degree of your pet's tumor disease.
Local treatments include surgical removal of the tumor and radiation therapy. The latter is used when a tumor cannot be completely removed surgically or to reduce the size of the tumor before surgery. For tumors that are particularly sensitive to radiation, radiation therapy is also used as the sole treatment. If surgical removal would involve significant risks or an unsatisfactory cosmetic result, radiation therapy is also the treatment of choice.
If local treatment is not possible, such as in the case of blood or bone marrow cancer, or if tumors have already metastasized to many other organs, chemotherapy may be considered. This involves fighting the tumor cells with drugs that act throughout the body.
Immunotherapy supports the immune system in fighting tumors. This involves administering drugs that strengthen the body's own immune defenses. In addition, it is advisable to strengthen the immune system through a balanced diet and, if necessary, with feed supplements. Your veterinary practice will be happy to advise you on this.
The prognosis depends on the malignancy of the tumor. A benign tumor has a good prognosis and in some cases does not require treatment. The more a tumor has already grown into the surrounding tissue or spread to other organs, the worse the prognosis. If many other organs are already affected by metastases in the advanced stage, euthanasia (see corresponding article) should be considered in order to spare your animal further suffering.
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