Home » Diseases » In dogs » Chronic Lymphocytic Leukemia, CLL (Cancer of the Lymphatic System)

Chronic Lymphocytic Leukemia, CLL (Cancer of the Lymphatic System) in Dogs

Occurrence: rarer
Location of illness: General/Whole body

Author: Dr. med. vet. Gisa Löwe | Last modified: 06.11.2025

ChronicChronic refers to a condition or disease that is long-lasting or permanent. Chronic diseases often develop slowly and can lead to persistent or recurring health problems over time. LymphocyticLymphocytic refers to lymphocytes, a type of white blood cell that plays an essential role in the body's adaptive immune response. The term is often used to describe the composition of cell populations in tissues or fluids. Leukemia (CLL) is a slowly progressing cancerCancer refers to the uncontrolled proliferation of cells that can lead to tumors or spread throughout the body. Various types of cancer occur in dogs and cats, ranging from skin cancer to lymphomas. of the lymphatic system in dogs, characterized by the uncontrolled proliferation of abnormal, mostly mature lymphocytesLymphocytes are a group of white blood cells crucial for the body's adaptive immune response. There are different types, including B cells, T cells, and natural killer cells, each with specific functions in the immune system. in the blood and bone marrow.

The most important facts at a glance

Chronic lymphocytic leukemia (CLL) in dogs is a cancerCancer refers to the uncontrolled proliferation of cells that can lead to tumors or spread throughout the body. Various types of cancer occur in dogs and cats, ranging from skin cancer to lymphomas. of the lymphatic system in which lymphocytesLymphocytes are a group of white blood cells crucial for the body's adaptive immune response. There are different types, including B cells, T cells, and natural killer cells, each with specific functions in the immune system., a type of white blood cell, proliferate uncontrollably. This leads to an accumulation in the blood and other tissues. The exact causes are not fully known, but genetic factors and possibly environmental factors such as exposureExposure refers to the Contact with or subjection to certain substances, environmental factors, or pathogens. In veterinary medicine, this can include Contact with toxins, allergens, or infectious agents that can cause health problems in dogs and cats. to chemicals may play a role. Symptoms can include enlarged lymph nodes, pale mucous membranes, increased susceptibility to infectionAn infection is the colonization and multiplication of pathogens such as bacteria, viruses, fungi, or parasites in an organism, which often, but not always, leads to a disease., and occasionally fever or bruising. DiagnosisA diagnosis is the identification of a disease or condition by its symptoms and/or results from diagnostic tests. It is the first step in the management and treatment of patients. is made by physical examination, blood tests, and possibly a bone marrow examination. ImmunophenotypingImmunophenotyping is a laboratory technique used to identify specific surface markers on cells. This technique is particularly important in the diagnosis and treatment of blood diseases and immune disorders in dogs and cats. can help determine the specific type of lymphocyte. Treatment depends on the disease progressionProgression refers to the advancement or worsening of a disease over time. It describes an increase in the severity or extent of the disease symptoms. and the health of the dog and may include an observation strategy or chemotherapyChemotherapy refers to the treatment of diseases, especially cancer, with chemical substances or drugs. It aims to kill cancer cells or prevent their growth, but can also affect healthy cells. with drugs such as chlorambucil and prednisone. Regular monitoring is crucial. The prognosisThe prognosis is the prediction of the likely course and outcome of a disease based on the general state of health, the nature of the disease, and the response to treatment. It can provide information on how a disease is expected to develop. varies greatly, depending on the response to treatment and other factors. Since the causes are not fully understood, there are no specific preventionPrevention includes measures taken to prevent diseases or injuries. In veterinary medicine, this includes vaccinations, parasite control, and health monitoring. measures, but a healthy lifestyle and regular veterinary check-ups can minimize the risk. Research focuses on genetic and molecular mechanisms of the disease, new diagnostic tools, and treatment approaches such as personalized medicine.

Causes

The lymphatic system of dogs includes lymph nodes, spleen, thymus, and bone marrow. It plays an essential role in the immune systemThe immune system is the body's defense system against infectious agents such as bacteria, viruses, fungi, and parasites. It comprises a complex network of organs, cells, and molecules that work together to protect the body. by helping to fight off infections and dispose of abnormal cells. LymphocytesLymphocytes are a group of white blood cells crucial for the body's adaptive immune response. There are different types, including B cells, T cells, and natural killer cells, each with specific functions in the immune system., a type of white blood cell, are crucial players in this system. In CLL, lymphocytesLymphocytes are a group of white blood cells crucial for the body's adaptive immune response. There are different types, including B cells, T cells, and natural killer cells, each with specific functions in the immune system. proliferate uncontrollably, leading to their accumulation in the blood and other tissues.

The exact causes of CLL development in dogs are not yet fully understood. Genetic factors appear to play a role, as certain breeds are more susceptible to developing the disease. Environmental factors, such as exposure to certain chemicals or radiation, may also play a role, but the evidence for this is limited.

Another possible factor is the dog’s own immune systemThe immune system is the body's defense system against infectious agents such as bacteria, viruses, fungi, and parasites. It comprises a complex network of organs, cells, and molecules that work together to protect the body.. An overactive or dysregulated immune systemThe immune system is the body's defense system against infectious agents such as bacteria, viruses, fungi, and parasites. It comprises a complex network of organs, cells, and molecules that work together to protect the body. can lead to uncontrolled cell proliferation. While acuteAcute refers to a condition that occurs suddenly and is usually of short duration. In a medical context, it describes symptoms or illnesses that can quickly become serious and require immediate attention. leukemias often arise from genetic mutations in precursor cells, CLL is typically associated with more mature lymphocytesLymphocytes are a group of white blood cells crucial for the body's adaptive immune response. There are different types, including B cells, T cells, and natural killer cells, each with specific functions in the immune system..

Symptoms

Very common symptoms:

Common symptoms:

Rare symptoms:

The symptoms of CLL are often subtle and develop slowly, making early detection difficult. The most common signs include general weakness and lethargy, which can be caused by anemia and a reduced ability to fight off infections. Weight loss and loss of appetite are also common symptoms.

Some dogs show swollen lymph nodes, which may be noticeable on physical examination. Occasionally, there may also be increased thirst and frequent urination, which may indicate impaired kidney function. In advanced cases, dogs may also show respiratoryRespiratory refers to breathing or the process of breathing. Respiratory diseases affect the respiratory tract and can impair the ability to breathe effectively. distress or bleeding due to impaired blood clotting.

Because the symptoms are so varied and non-specific, it is important to perform a thorough diagnostic evaluation if CLL is suspected.

Diagnosis

The diagnosisA diagnosis is the identification of a disease or condition by its symptoms and/or results from diagnostic tests. It is the first step in the management and treatment of patients. of CLL usually begins with a thorough physical examination and the collection of the dog’s medical history. Blood tests are crucial to assess the number and appearance of lymphocytesLymphocytes are a group of white blood cells crucial for the body's adaptive immune response. There are different types, including B cells, T cells, and natural killer cells, each with specific functions in the immune system.. A complete blood count may show elevated lymphocyte counts (lymphocytosis) and signs of anemia or thrombocytopeniaThrombocytopenia is a condition in which the number of platelets in the blood is lower than normal, increasing the risk of mild to severe Bleeding..

A bone marrow examination may be required to confirm the diagnosisA diagnosis is the identification of a disease or condition by its symptoms and/or results from diagnostic tests. It is the first step in the management and treatment of patients.. This involves taking a sample of the bone marrow and examining it for the presence of abnormal lymphocytesLymphocytes are a group of white blood cells crucial for the body's adaptive immune response. There are different types, including B cells, T cells, and natural killer cells, each with specific functions in the immune system.. In addition, imaging procedures such as ultrasoundUltrasound refers to sound waves that are above the hearing threshold of the human ear. In medicine, ultrasound is used for diagnostic imaging procedures to visualize internal organs, tissues, and blood flow. or X-rays can be performed to rule out or confirm involvement of internal organs.

ImmunophenotypingImmunophenotyping is a laboratory technique used to identify specific surface markers on cells. This technique is particularly important in the diagnosis and treatment of blood diseases and immune disorders in dogs and cats., a special laboratory method, can be used to determine the specific type of lymphocytesLymphocytes are a group of white blood cells crucial for the body's adaptive immune response. There are different types, including B cells, T cells, and natural killer cells, each with specific functions in the immune system. involved in the leukemia. This can help clarify the prognosisThe prognosis is the prediction of the likely course and outcome of a disease based on the general state of health, the nature of the disease, and the response to treatment. It can provide information on how a disease is expected to develop. and choose the best therapeutic strategy.

Therapy

The treatment of CLL in dogs is complex and depends on various factors, including the progressionProgression refers to the advancement or worsening of a disease over time. It describes an increase in the severity or extent of the disease symptoms. of the disease, the overall health of the dog, and the owner’s preferences. An observation strategy may be considered in asymptomaticAsymptomatic means that there are no recognizable symptoms of a disease. An animal can have a disease or infection without showing visible signs, which can make diagnosis and treatment more difficult. dogs with stable disease burden. In more advanced cases, chemotherapyChemotherapy refers to the treatment of diseases, especially cancer, with chemical substances or drugs. It aims to kill cancer cells or prevent their growth, but can also affect healthy cells. may be required.

ChemotherapyChemotherapy refers to the treatment of diseases, especially cancer, with chemical substances or drugs. It aims to kill cancer cells or prevent their growth, but can also affect healthy cells. for CLL aims to control the proliferation of lymphocytesLymphocytes are a group of white blood cells crucial for the body's adaptive immune response. There are different types, including B cells, T cells, and natural killer cells, each with specific functions in the immune system. and alleviate symptoms. Commonly used medications include chlorambucil and prednisone. These medications can be administered orally and have relatively few side effects compared to other chemotherapyChemotherapy refers to the treatment of diseases, especially cancer, with chemical substances or drugs. It aims to kill cancer cells or prevent their growth, but can also affect healthy cells. protocols.

In addition to chemotherapyChemotherapy refers to the treatment of diseases, especially cancer, with chemical substances or drugs. It aims to kill cancer cells or prevent their growth, but can also affect healthy cells., supportive treatments such as blood transfusions or antibiotics may be necessary to combat infections. Regular monitoring through blood tests is crucial to assess the effectiveness of the treatment and to react to changes early on.

Prognosis and follow-up care

The prognosis for dogs with CLL varies considerably. Some dogs live for several years after diagnosisA diagnosis is the identification of a disease or condition by its symptoms and/or results from diagnostic tests. It is the first step in the management and treatment of patients. with minimal symptoms, while others experience a more rapid deterioration. Life expectancy can be improved through regular veterinary care and individual adaptation of the therapyTherapy refers to the treatment of diseases or disorders with the aim of alleviating symptoms, promoting healing, or improving quality of life. Therapies can be medicinal, surgical, or through other medical interventions..

Factors that influence the prognosisThe prognosis is the prediction of the likely course and outcome of a disease based on the general state of health, the nature of the disease, and the response to treatment. It can provide information on how a disease is expected to develop. include the level of the lymphocyte count, the presence of anemia or thrombocytopeniaThrombocytopenia is a condition in which the number of platelets in the blood is lower than normal, increasing the risk of mild to severe Bleeding., and the response to treatment. Dogs that respond well to therapyTherapy refers to the treatment of diseases or disorders with the aim of alleviating symptoms, promoting healing, or improving quality of life. Therapies can be medicinal, surgical, or through other medical interventions. tend to have a better prognosisThe prognosis is the prediction of the likely course and outcome of a disease based on the general state of health, the nature of the disease, and the response to treatment. It can provide information on how a disease is expected to develop..

Long-term survival rates are difficult to predict, as they depend on many variable factors. Close collaboration with a veterinarian specializing in oncologyOncology is the branch of medicine that deals with the diagnosis, treatment, and research of cancer. In veterinary medicine, this includes the treatment of cancers in animals. can help create the best treatment plan and optimize survival.

Prevention

Since the exact causes of CLL are not fully understood, there are no specific measures to prevent the disease. However, general measures to promote the dog’s health can help minimize the risk of cancer and other diseases.

These include a balanced diet, regular exercise, and avoidance of environmental toxins. Regular veterinary check-ups are important to detect and treat health problems early.

For breeders, it may be useful to pay attention to genetic predispositions and exclude affected animals from breeding in order to reduce the risk of disease transmission. Even if this cannot prevent the development of CLL, it could reduce the incidenceIncidence refers to the number of new cases of a disease or condition that occur within a specific time period in a specific population group. It provides information about the risk of contracting the disease. of the disease in certain breeds in the long term.

Outlook on current research

Research into ChronicChronic refers to a condition or disease that is long-lasting or permanent. Chronic diseases often develop slowly and can lead to persistent or recurring health problems over time. LymphocyticLymphocytic refers to lymphocytes, a type of white blood cell that plays an essential role in the body's adaptive immune response. The term is often used to describe the composition of cell populations in tissues or fluids. Leukemia (CLL) in dogs is in a constant state of development, focusing on both diagnostic methods and treatment options. Current studies aim to better understand the genetic and molecular mechanisms that lead to the development and progressionProgression refers to the advancement or worsening of a disease over time. It describes an increase in the severity or extent of the disease symptoms. of CLL. Researchers have begun to analyze in more detail the genetic abnormalities that occur in dogs with CLL. By comparing with human databases, scientists hope to find parallels that could lead to better diagnostic and therapeutic approaches.

Another important area of research is the development of new diagnostic tools that could enable more accurate and earlier detection of CLL. For example, advanced imaging techniques and improved blood tests are being developed to detect the disease at the earliest possible stage. Research is also focusing on the role of the immune systemThe immune system is the body's defense system against infectious agents such as bacteria, viruses, fungi, and parasites. It comprises a complex network of organs, cells, and molecules that work together to protect the body. in the development of CLL, as the behavior of immune cellsImmune cells are specialized cells of the immune system that help to identify and fight pathogens and foreign substances. These include leukocytes such as lymphocytes (T cells and B cells), macrophages, and dendritic cells. plays a significant role in the disease. New immunotherapeutic approaches are being tested to see if they can slow down or even stop the progressionProgression refers to the advancement or worsening of a disease over time. It describes an increase in the severity or extent of the disease symptoms. of the disease.

With regard to treatment, various chemotherapeutic agents and targeted therapies are currently being tested. Some of these drugs are already in use in human medicine, and research is trying to find out whether they are also safe and effective for dogs. An area of particular interest is personalized medicine, where treatment is individually tailored to the genetic characteristics of a dog’s tumorA tumor is an abnormal growth of tissue that can be benign or malignant. Tumors can develop in any part of the body and affect various functions.. This could lead to customized therapyTherapy refers to the treatment of diseases or disorders with the aim of alleviating symptoms, promoting healing, or improving quality of life. Therapies can be medicinal, surgical, or through other medical interventions. plans in the future that significantly improve the quality of life and survival rate of affected dogs.

In addition, research is investigating the role of nutrition and supportiveSupportive refers to supportive treatments that aim to alleviate symptoms and improve quality of life without directly treating the underlying cause of the disease. care. There is evidence that certain diets and nutritional supplements may play a supportiveSupportive refers to supportive treatments that aim to alleviate symptoms and improve quality of life without directly treating the underlying cause of the disease. role in the treatment of CLL. Long-term studies are underway to determine how lifestyle changes and diets might affect the progressionProgression refers to the advancement or worsening of a disease over time. It describes an increase in the severity or extent of the disease symptoms. of the disease.

Overall, current research shows that a multidisciplinary approach is necessary to address the complex challenges in the treatment of CLL in dogs. Future advances in research could lead to better diagnostic options and more effective treatment plans that could improve the lives of many affected dogs.

Frequently asked questions (FAQs)

What is ChronicChronic refers to a condition or disease that is long-lasting or permanent. Chronic diseases often develop slowly and can lead to persistent or recurring health problems over time. LymphocyticLymphocytic refers to lymphocytes, a type of white blood cell that plays an essential role in the body's adaptive immune response. The term is often used to describe the composition of cell populations in tissues or fluids. Leukemia (CLL) in dogs? ChronicChronic refers to a condition or disease that is long-lasting or permanent. Chronic diseases often develop slowly and can lead to persistent or recurring health problems over time. lymphocyticLymphocytic refers to lymphocytes, a type of white blood cell that plays an essential role in the body's adaptive immune response. The term is often used to describe the composition of cell populations in tissues or fluids. leukemia is a cancerCancer refers to the uncontrolled proliferation of cells that can lead to tumors or spread throughout the body. Various types of cancer occur in dogs and cats, ranging from skin cancer to lymphomas. of the lymphatic system in which there is an overproduction of abnormal lymphocytesLymphocytes are a group of white blood cells crucial for the body's adaptive immune response. There are different types, including B cells, T cells, and natural killer cells, each with specific functions in the immune system.. These cells can weaken the immune systemThe immune system is the body's defense system against infectious agents such as bacteria, viruses, fungi, and parasites. It comprises a complex network of organs, cells, and molecules that work together to protect the body. and impair the healthy function of organs.
What symptoms can occur in dogs with CLL? The symptoms of CLL can be non-specific and include loss of appetite, weight loss, lethargy, enlarged lymph nodes, fever, and occasionally increased thirst or urination.
How is CLL diagnosed in dogs? The diagnosisA diagnosis is the identification of a disease or condition by its symptoms and/or results from diagnostic tests. It is the first step in the management and treatment of patients. is usually made by blood tests, which reveal an unusually high number of lymphocytesLymphocytes are a group of white blood cells crucial for the body's adaptive immune response. There are different types, including B cells, T cells, and natural killer cells, each with specific functions in the immune system.. A bone marrow examination may also be necessary to confirm the diagnosisA diagnosis is the identification of a disease or condition by its symptoms and/or results from diagnostic tests. It is the first step in the management and treatment of patients..
What treatment options are available for dogs with CLL? Treatment may include chemotherapyChemotherapy refers to the treatment of diseases, especially cancer, with chemical substances or drugs. It aims to kill cancer cells or prevent their growth, but can also affect healthy cells., immunotherapy, or supportiveSupportive refers to supportive treatments that aim to alleviate symptoms and improve quality of life without directly treating the underlying cause of the disease. care. The choice of treatment depends on various factors, including the stage of the disease and the general health of the dog.
What is the prognosisThe prognosis is the prediction of the likely course and outcome of a disease based on the general state of health, the nature of the disease, and the response to treatment. It can provide information on how a disease is expected to develop. for dogs with CLL? The prognosisThe prognosis is the prediction of the likely course and outcome of a disease based on the general state of health, the nature of the disease, and the response to treatment. It can provide information on how a disease is expected to develop. can vary. Some dogs live for several years with the disease, while others experience a faster progressionProgression refers to the advancement or worsening of a disease over time. It describes an increase in the severity or extent of the disease symptoms.. Regular veterinary monitoring and appropriate treatment can improve the quality of life.
Can all dog breeds develop CLL? Yes, all dog breeds can develop CLL, although it is more common in older dogs. There is no specific breed predispositionA predisposition is an innate inclination or susceptibility of an organism to certain diseases or conditions. In dogs and cats, there may be a genetic predisposition to certain conditions such as hip dysplasia or certain heart diseases. for this disease.
Is CLL curable in dogs? Currently, there is no cure for CLL in dogs, but the disease can often be controlled by various treatments to improve the dog’s quality of life and extend life expectancy.
Are there preventive measures against CLL in dogs? There are no specific preventive measures, but a healthy lifestyle, regular veterinary check-ups, and a balanced diet can contribute to general health and help detect the disease early.
How does CLL affect a dog’s daily life? The effects vary depending on the severity of the disease. Some dogs show few symptoms and have a good quality of life, while others may experience significant limitations. Treatment can help alleviate the symptoms.
What role does nutrition play in the treatment of CLL? A balanced diet can support the immune systemThe immune system is the body's defense system against infectious agents such as bacteria, viruses, fungi, and parasites. It comprises a complex network of organs, cells, and molecules that work together to protect the body. and contribute to general health. Some studies suggest that certain diets may positively influence the course of the disease, but further research is needed to provide specific recommendations.

When to visit the vet?

If the condition worsens / symptoms persist, consult a veterinarian.