Lymphoma is a cancer type that occurs when lymphocytes known as white blood cells become malignant. Lymphocytes under normal circumstances are cells of the immune system that help your dog fight against infections. They live in the lymph nodes which is a complex system connected by webs of veins. This system is responsible for recognizing and destroying foreign proteins and infection causes in the body. Lymphocytes are organized all throughout the body for this responsibility therefore in case of lymphoma, they may cause lesions almost anywhere in the body. Disease can appear in primary lymphoid organs such as the lymph node, liver, spleen, bone marrow in the lymphatic system or any organ where they are located for defending the body such as eye, skin or the digestive system.
Lymphoma is a frequently encountered cancer compared to other types of cancers in dogs with a ratio of 1/8. There are more than thirty types of lymphomas all of which vary radically in behavior. Some of them unless treated progress very rapidly and become life threatening in a matter of weeks whereas some progress very slowly; they are easily kept under control and the patient may survive for years. In literature regarding lymphoma in dogs, for 5% of them, particularly if it is localized it is accepted that a full recovery is possible.
The multicentric form of lymphoma arises in primary lymphoid organs such as lymph nodes, spleen, liver or the bone marrow. It is similar to non-Hodgkin’s lymphoma (NHL) in humans both histopathologically and in terms of its response to chemotherapy protocols. That is why the success in treating lymphoma in dogs increase in parallel to the success in treating lymphoma in humans.
As a pet owner whose dog is suffering from lymphoma, I am sure you are curious as to how the disease works. Unfortunately, the reason for the disease has not been revealed completely as it was in other types of cancers. But it is believed that chronic diseases that suppress the immune system, viruses and chemical agents all play a role in the disease.
Lymphoma can arise in all breeds and ages of dogs. There is however a higher risk for older dogs aged 6 or higher. Although we encounter the disease most commonly in Rottweilers, Golden Retrievers, Labrador Retrievers and Scottish Retrievers are also under risk.
How are lymphomas classified?
Lymphomas are initially classified according to the organ they arise in.
1. Multicentric Lymphoma: It begins in primary lymphoid organs, lymph nodes, spleen, liver and unless treated it might aggressively spread to the bone marrow and the nervous system. It is the form similar to non-Hodgkin’s lymphoma (NHL) in humans. Clinically, it is the most commonly encountered form and its treatment protocols and prognosis are the most precise.
2. Alimentary Lymphoma: Although it mostly appears in cats, incidence in dogs is also very high. Malignancy appears in the stomach, intestines, liver and the lymph nodes responsible for defending them. It is difficult to diagnose but there is a higher rate of success in treatment and survival compared to the multicentric form.
3. Mediastinal Lymphoma: It arises in the thymus gland in the chest cavity and suppresses breathing, therefore it causes more severe symptoms. Increased calcium levels in mediastinal lymphomas are very important because histopathologically they point to a T cell lymphoma. This form is also called thymic lymphoma.
4. Cutaneous Lymphoma: This form is the most frequently misdiagnosed type of lymphoma which appears on the skin. If the histopathology of cutaneous lymphoma has T cell origins the success rate for treatment is fairly low. Under these circumstances, the chemotherapy protocols vary.
5. Acute Lymphoblastic Lymphoma: Disease starts in the bone marrow and a bone narrow sample is required for diagnosis.
It is possible to encounter lymphoma in kidneys, nervous system, nasal cavity, in-mouth, subcutaneously albeit less commonly. In these areas, if a single lesion is detected, a full recovery is possible with techniques such as radiotherapy if the histopathological origin is suitable for treatment.
Secondarily, lymphomas are classified histopathologically according to their types and behavior by immunostaining.
Disease is divided into two categories as T and B cells depending on the cell group origins of the lymphocytes. As a result, your veterinary can decide on the treatment protocol according to lymphoma’s behavior.
How do I know if my dog has lymphoma?
This is a very difficult question. It depends on the form and the stage of the lymphoma of the dog.
Multicentric lymphoma: It initially appears by noticeable swelling of one or more of the lymph nodes of your dog. These swellings do not cause pain, they are hard and slide under the skin. At this stage, most dogs do not show any clinical symptoms, there are also no abnormal results in their blood tests. But it is very important to diagnose lymphoma at this stage for the survival of the dog. Pet owners unfortunately lose time at this stage since the dog shows no symptoms, however a simple cytological sample can change the fate of the animal. If the lymphoma is not detected at this stage, it will progress and the dog will show symptoms of fever, loss of appetite, vomiting, difficulty breathing, polydipsia and problems in toilet behavior. At this point, it is typical to have edema in the feet. As the disease progresses dog will suffer from weight loss due to not being able to eat, skin issues, and cardiac problems. If the disease is still not treated, the dog will be vocal about pain, hemorrhage and sometimes there will be bleeding through the natural cavities such as nasal cavity. It may also result in sudden death. In some forms, this period may last weeks and in others, months.
Cutaneous Lymphoma (Skin Lymphoma): Skin lymphoma is the most confusing type of lymphoma for the veterinary. It starts out as a regular allergic skin disease we frequently encounter and veterinaries focus on a possible allergic or fungal reaction factor for months. Itchy and ulcerated skin lesions can appear in any skin area. When it appears on gums, it may be confused with periodontal diseases. Although it leads the veterinary to redirect her attention to deeper diagnostic procedures when the lesions are more rubescent and itchier than normal, it is still baffling.
Alimentary Lymphoma: This disease starts out like a regular gastrointestinal disease yet is resistant to symptomatic treatment. Symptoms include vomiting and weight loss like any other gastrointestinal disease but sometimes one can observe diarrhea and black, smelly stool. Diagnosis is possible through biopsy and advanced imaging techniques.
Mediastinal Lymphoma: It is revealed through difficulty in breathing due to a mass in the chest cavity. Because the lymphoid tissue cannot function properly, the increasing pleural effusion will make respiration more difficult. Sometimes there is swelling on the face and front legs. This form causes polydipsia and frequent urination.
How can I be sure my dog has lymphoma?
The only procedure for a certain diagnosis of lymphoma is a biopsy sample to be taken from the area under suspicion. Before this procedure, your veterinary will analyze the cytological samples taken with fine needle yet a histopathological classification and the decision for the correct medication protocol depends on the result of the biopsy. Depending on the biopsy method, the dog should be sedated or put under deep anesthesia. Depending on the location of the lesion, a trucut biopsy or the partial or complete removal of the lymph node with the lesion might be necessary. These procedures generally cause no pain or complication. Depending on the procedure, pain medication can be prescribed to prevent pain.
Aside from biopsy, are any other diagnostic procedures necessary?
Determining the stage of your dog’s lymphoma is important to present the correct prognosis and decide on the treatment protocol. We routinely suggest urinalysis, blood tests, chest xrays and abdomen ultrasound for our patients. In some cases and types of lymphoma, we might also request bone marrow aspiration, cerebrospinal fluid analysis and advanced imaging techniques such as PET-scan. These procedures enable us to better understand to disease in order to treat it in a multifaceted manner. Advanced imaging techniques can be especially life saving in patients whose lymphomas are localized that require radiotherapy.
How do you treat lymphoma?
The most appropriate treatment for lymphoma is chemotherapy. Depending on the location of the lymphoma, radiotherapy and surgical operation are also options. In some cases, all three treatments can be used together in order to manage a treatment protocol that has the least amount of side effects for the patient. The general condition of the animal and the pet owner’s compliance are also factors taken into consideration when determining the treatment protocol.
Different chemotherapeutic agents are used weekly in lymphoma and the treatment lasts for 20 or more weeks making the least amount of side effects and best chances of survival possible. These protocols lengthen the remission periods of the patient but if the pet owner does not wish to comply, they can be replaced by single-agent chemotherapy. But under these circumstances, chances of survival drop by almost 50%.
Multicentric lymphomas respond to chemotherapy by 90% and the disease goes into remission. Remission is a period when your dog is completely healthy and spends high quality time with you. The length of this period depends on the stage and type of lymphoma.
How is chemotherapy given and how long does it last?
Although chemotherapy can be administered in different ways depending on the disease, it is usually given intravenously. Protocols vary but it requires the patient to come to the clinic once a week. The whole procedure lasts for 2-3 hours. After a complete blood count the patient is given drugs for premedication and then chemotherapy is administered.
Will my dog feel bad after chemotherapy? Does it entail any risks?
Compared to people, dogs show fewer side effects after chemotherapy. The reason for this is that it is administered to dogs in much lower doses. In veterinary medicine, survival time and life quality are equally important. In order to prevent gastrointestinal problems such as nausea and allergic reactions, the medication given before chemotherapy is essential. Despite all precautions 5% of dogs may experience decrease in activity and stomach issues for 1-2 days which can be taken under control. Yet dogs do not present with side effects such as hair loss like humans.
Some breeds of dogs such as Collie have multidrug resistance gene and show severe symptoms to some medication used during chemotherapy. These breeds are tested for this gene by a genetic test abroad and when necessary their protocols are modified. When we change the medication protocols of patients after a request from the pet owner, we assist them in getting such a test done. Although the possibility of carrying this gene for your dog depends on the breed, all breeds might be prone to this problem.
One of the most frequently encountered side effects in dogs is the suppression of the bone marrow. In these cases hormonal applications to reactivate the bone marrow might be necessary depending on the severity of the symptoms.
Is it possible for my dog to recover from lymphoma?
This depends on the type of lymphoma. Localized lymphomas have the highest rates for recovery and a full recovery chance of 5% is expected. But lymphomas generally go into remission right after treatment. This period lasts from 9 to 13 months depending on the stage and histopathological type of disease. When it reappears, it might again be forced into remission for half the period as the first one, on average of 2 months, with relapse protocols. These protocols last shorter than the first ones and are applied with different medication. When the patient develops resistance for chemotherapy, it leads to death. It is possible to provide a survival of 4 or more years with 2-agent chemotherapy in indolent lymphomas. Although one aims at 2 years at a time, even 1 year of healthy life is considered a success. The time period changes according to the stage and histopathological classification. Depending on the staging and the treatment done by your veterinary, it is easier to predict how long this period is going to be. Compared to T cell lymphomas, B cell lymphomas respond better to treatment.
One should always bear in mind that even if lymphoma cannot be cured, your dog’s life span may be lengthened with treatment and you will have had a peaceful, happy and relatively long time with your dog by the time you say your goodbyes. When a treatment is not affordable, single agent cortisone use will lengthen your dog’s life and make his passing away less painful and easier.
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