What Is Lymphoma in Dogs?
Lymphoma, also referred to as lymphosarcoma (LSA), stands as one of the prevalent cancers observed in dogs. This condition emerges from the excessive proliferation and lack of regulation in lymphocytes, pivotal cells responsible for bolstering the immune system and defending the body against infections. While lymphosarcoma can manifest in various organs, its primary impact is on components of the immune system, encompassing the lymphatic system, lymph nodes, spleen, and bone marrow. Given the interconnectedness of the lymphatic system with the bloodstream, lymphosarcoma is categorized as a systemic ailment, necessitating systemic interventions such as chemotherapy for effective treatment.
Types
In dogs, lymphoma presents itself in various forms, each affecting different organs. The primary types include:
- Multicentric Lymphoma: Initially noticed in the lymph nodes.
- Gastrointestinal Lymphoma: Targets the stomach and intestines.
- Cutaneous Lymphoma: Affects the skin.
Less prevalent variations of lymphoma in dogs consist of:
- Extranodal Lymphoma: Occurring when lymphoma develops in organs beyond the lymphatic system, such as the eye or kidney.
- Mediastinal Lymphoma: A rare occurrence where lymphoma impacts the lymphoid organs within the chest cavity, such as the thymus.
Symptoms
Lymphoma, also known as lymphosarcoma (LSA), manifests in dogs with the most common symptom being the enlargement of lymph nodes that feel firm and painless upon touch. Dogs have various pairs of lymph nodes across their bodies, with the prescapular (front of chest), submandibular (under the jaw), and popliteal (behind the knees) nodes being the easiest to locate and examine. Typically, one or more nodes become enlarged.
In addition to lymph node enlargement, dogs with LSA may exhibit the following symptoms:
- Weight loss
- Decreased appetite
- Swelling of the face or limbs
- Increased thirst and urination
Specific symptoms may arise depending on the area of the body affected:
- Dry, crusty skin with patches of hair loss, loss of color, and ulcerated skin for cutaneous LSA
- Diarrhea and vomiting for gastrointestinal LSA
- Exercise intolerance, coughing, and difficulty breathing for mediastinal LSA.
Causes
The causes of cancer, including lymphoma in dogs, often remain poorly understood. Various factors have been linked to the development of certain cancers, such as:
- Age
- UV damage or other environmental factors
- Specific viruses and infections
- DNA mutations
- Genetics
It’s important to note that cancer typically arises due to a combination of these factors rather than a single cause. The development of lymphoma follows this pattern as well.
Diagnosis
In most instances, the initial indication of lymphosarcoma (LSA) in dogs is the presence of enlarged lymph nodes. Following this observation, your veterinarian might opt for a cytology procedure (using a needle to extract cells from the node) or a biopsy (employing a larger needle to obtain cell samples or tissue chunks from the node) for examination by a pathologist.
Once your dog receives a diagnosis, your veterinarian may suggest additional examinations or refer you to an oncologist for further assessments and treatment planning. This may involve staging procedures to determine the extent of cancer spread, including chest x-rays, abdominal ultrasound, blood tests, bone marrow aspirates, and IHC (immunohistochemistry) or flow cytometry to identify the specific type of lymphoma.
Stages of Lymphoma in Dogs
Lymphosarcoma (LSA) in dogs is categorized into five stages based on the extent of involvement across body systems:
- Stage I: Involvement of a single lymph node
- Stage II: Multiple lymph nodes affected within a similar region
- Stage III: All lymph nodes throughout the body are affected
- Stage IV: In addition to lymph node involvement, organs such as the spleen, liver, and chest are affected
- Stage V: Bone marrow is involved
Treatment
Lymphoma stands out as one of the cancers highly responsive to chemotherapy in dogs, with remission achievable in well over 50% of cases. Dogs generally tolerate chemotherapy better than humans, often receiving lower doses with fewer anticipated side effects. The treatment’s objective is to maintain your dog’s quality of life for as long as possible. While some side effects like decreased appetite, lethargy, and mild vomiting and diarrhea may occur, serious complications such as bone marrow suppression and secondary infections are less common. Generally, dogs do not experience hair loss during chemotherapy.
An oncologist can guide the selection of the most suitable medication or combination of medications for your dog. Various chemotherapeutic drugs are employed in treating Lymphosarcoma (LSA), including Lomustine, Vincristine, Prednisone, Cyclophosphamide, Chlorambucil, and L-Asparaginase. In certain cases, surgical removal of affected lymph nodes or organs may be recommended by your veterinarian. If chemotherapy isn’t feasible, discussing the use of steroids alone, particularly Prednisone, with your veterinarian can help alleviate clinical signs and enhance your pet’s comfort, even if only for a brief period.
Despite aggressive treatment, Lymphosarcoma (LSA) cannot be cured, and relapse is common in most dogs. Some dogs may achieve a second remission, although it’s more challenging. Humane euthanasia may be suggested when the cancer and its effects become uncontrollable.
Living and Management
While Lymphosarcoma (LSA) can be managed and may enter remission, complete eradication is not typically achievable. Anticipate the likelihood of cancer recurrence, necessitating another round of chemotherapy, often with a different protocol than before, to achieve remission, a task that can be quite challenging. Your veterinarian should conduct frequent examinations of your dog for signs of relapse, often indicated by enlarged lymph nodes. It’s crucial to adhere to recommendations for follow-up exams and testing.
Moreover, prioritize your dog’s quality of life over mere quantity when dealing with LSA. Side effects and treatments are usually less severe compared to human medicine, allowing dogs to maintain a normal, happy, and positive life throughout treatment and follow-ups.
Lymphoma in Dogs FAQs
Are there ways to prevent lymphoma in dogs?
Regrettably, lymphoma cannot be prevented. However, regular checkups and attentive observation at home are essential for early detection and treatment.
What is the life expectancy of a dog with lymphoma?
The life expectancy of dogs with lymphoma varies. Without treatment, the average survival time is 4–6 weeks. Around 50% of dogs will survive beyond this period, while approximately 50% will succumb before it. For dogs undergoing chemotherapy, the average survival time extends to about a year.