Large Cell Lymphoma in Dogs: An Overview of the Disease

Large cell lymphoma in dogs represents a serious form of cancer impacting the lymphatic system, a network of tissues and organs that help rid the body of toxins, waste, and other unwanted materials. This disease originates from lymphocytes, a type of white blood cell. Though concerning, lymphoma is often manageable with various treatment options. Early recognition of signs and prompt veterinary intervention can improve outcomes and well-being.

Understanding Large Cell Lymphoma

Large cell lymphoma is a cancer of lymphocytes, immune system cells that defend the body against viruses and bacteria. When these lymphocytes mutate and proliferate abnormally, they can form tumors within the lymphatic system and other organs. This form of lymphoma is aggressive, progressing quickly if untreated.

Lymphoma in dogs can manifest in several ways, depending on where the cancerous cells primarily accumulate. The most common form, multicentric lymphoma, affects multiple lymph nodes throughout the body, accounting for 80-85% of all canine lymphoma cases. Other forms include gastrointestinal lymphoma (stomach and intestines), cutaneous lymphoma (skin), and mediastinal lymphoma (chest lymphoid organs like the thymus).

Recognizing the Signs

The clinical signs of large cell lymphoma in dogs can vary significantly based on the affected body region. For multicentric lymphoma, the most common sign is enlarged peripheral lymph nodes, felt as firm, rubbery, non-painful lumps under the skin. These enlarged nodes are often found under the jaw (submandibular), in front of the shoulders (prescapular), or behind the knees (popliteal). They can be three to ten times larger than their normal size.

Beyond swollen lymph nodes, dogs with multicentric lymphoma may also show general signs like decreased appetite, lethargy, and weight loss. Some dogs may experience swelling in the face or legs, or an increase in thirst and urination. When the disease affects specific organs, the symptoms become more localized. For instance, gastrointestinal lymphoma can cause vomiting, diarrhea, and abdominal pain. Mediastinal lymphoma may lead to breathing difficulties or coughing. Cutaneous lymphoma often appears as dry, flaky, red, itchy skin patches that can ulcerate.

Diagnosis and Staging

Diagnosis begins with a thorough physical examination by a veterinarian, especially if enlarged lymph nodes are present. A common initial step involves a fine needle aspirate (FNA) of an affected lymph node or mass. This minimally invasive procedure collects cells for cytological examination, which often confirms a lymphoma diagnosis within one to two days. If cytology results are inconclusive or more detailed information is needed, a biopsy of the lymph node or affected organ may be performed, with histopathology and immunohistochemistry the gold standard for definitive diagnosis and subtyping.

Once lymphoma is confirmed, staging tests are conducted to determine the extent of the disease throughout the body. This process helps guide treatment decisions and provides prognostic information. Common staging tests include a complete blood count (CBC), serum chemistry panel, and urinalysis to assess overall health and organ function. Imaging techniques such as thoracic radiographs (X-rays) and abdominal ultrasound are used to check for internal organ involvement, including the spleen, liver, and chest cavity. A bone marrow aspirate may also be performed.

Treatment Approaches and Prognosis

The primary treatment for large cell lymphoma in dogs is chemotherapy, as it is a systemic disease. The goal of chemotherapy is to achieve remission, the disappearance of all cancer signs, improving quality of life and extending lifespan. Dogs tolerate chemotherapy better than humans, with fewer and milder side effects due to lower dosages and a focus on quality of life. Side effects, if they occur, are mild and include decreased appetite, lethargy, or mild vomiting and diarrhea.

The most effective and commonly used multi-drug chemotherapy protocol is CHOP, which combines cyclophosphamide, doxorubicin (hydroxydaunorubicin), vincristine (oncovin), and prednisone/prednisolone. This protocol leads to high complete remission rates, ranging from 80-95%. While a permanent cure is rare, about 10% of dogs may achieve a long-term cure with combination chemotherapy. Median survival times for dogs treated with CHOP protocols are between 10 to 14 months, with some dogs living 12 to 24 months.

Prognosis is influenced by several factors, including the specific type of lymphoma (immunophenotype), the stage of the disease at diagnosis, and the dog’s overall health. B-cell lymphomas have a better prognosis and longer remission times compared to T-cell lymphomas. Dogs presenting with systemic illness (substage b) have a worse prognosis than those who appear clinically healthy (substage a). Prednisolone can provide temporary relief and even induce short remissions, but starting it before chemotherapy can lead to drug resistance and shorter survival times.

Indeterminate Pulmonary Nodules: Causes and Management

The AUDIT-C Screening Tool: Questions and Scoring

What Is Alcohol Detoxification & How Does It Work?