Lymphoma is a common and serious cancer in cats, representing a malignant transformation and unchecked growth of lymphocytes, a type of white blood cell central to the immune system. These cells are found throughout the body, meaning lymphoma can arise in almost any organ, though it most frequently affects the gastrointestinal tract. T-cell lymphoma specifically originates from T-lymphocytes, which normally mature in the thymus and are responsible for cell-mediated immunity. This form of cancer is characterized by its diversity in location and behavior, ranging from relatively slow-growing to highly aggressive presentations.
Understanding Feline T-Cell Lymphoma
Feline lymphoma is broadly categorized by the type of lymphocyte involved, either B-cells or T-cells. The specific behavior and prognosis of the cancer are heavily influenced by the anatomical location and the grade of the cells. The disease is often classified into distinct forms depending on where the tumor first develops, which determines the cat’s symptoms.
One of the most common forms observed today is the gastrointestinal or alimentary lymphoma, which is frequently a low-grade, small-cell T-cell type. This presentation typically affects older, Feline Leukemia Virus (FeLV)-negative cats and is often linked to chronic inflammation in the digestive tract.
In contrast, the aggressive mediastinal form of T-cell lymphoma develops in the chest cavity. This form is strongly associated with FeLV infection and is more common in younger cats, with up to 80% testing positive for the virus.
A mass in the mediastinum (the space between the lungs) can rapidly compress the heart and respiratory structures. T-cell lymphoma can also manifest in other extranodal sites, such as the nasal cavity or the kidneys.
Clinical Signs and Initial Suspicion
The observable signs of T-cell lymphoma vary widely because the cancer can affect multiple organ systems. These non-specific systemic changes often reflect the cat’s general malaise. Signs include weight loss, a decrease in appetite, and persistent lethargy, which can be easily mistaken for normal aging.
When the lymphoma is located in the gastrointestinal tract, the symptoms involve digestive upset. Cats may experience chronic vomiting and diarrhea, which can be intermittent and often persist for several months before diagnosis. High-grade gastrointestinal lymphoma may present with a palpable abdominal mass or a rapid onset of severe symptoms.
For tumors in the chest cavity, the mediastinal form causes signs related to respiratory distress. Affected cats may exhibit difficulty breathing (dyspnea) or rapid, shallow breathing (tachypnea) due to the tumor mass or fluid accumulation (pleural effusion) restricting lung expansion.
Nasal T-cell lymphoma, a localized form, presents with chronic, often bloody, nasal discharge, noisy breathing, or visible swelling of the face or bridge of the nose.
Confirming the Diagnosis
The diagnostic process begins with a thorough physical examination and laboratory tests to assess the cat’s overall health. A complete blood count, serum biochemistry profile, and urinalysis are performed to check for organ dysfunction and systemic changes. Testing for Feline Leukemia Virus (FeLV) and Feline Immunodeficiency Virus (FIV) is also performed, as a positive status significantly influences both prognosis and treatment choice.
To definitively confirm lymphoma, tissue samples from the affected area must be obtained. This is often done using fine-needle aspiration (FNA) to collect cells for cytology, allowing a veterinary pathologist to identify the malignant lymphocytes. If the FNA is inconclusive, a biopsy is required for histopathology, providing a more detailed structural and cellular analysis.
Further testing is needed to identify the T-cell phenotype and grade the tumor. Techniques like immunohistochemistry (IHC) or flow cytometry use specific markers, such as CD3, to confirm the T-cell lineage. Staging involves imaging with thoracic radiographs (X-rays) and an abdominal ultrasound to determine the extent of the cancer and check for spread. The distinction between low-grade (small cell) and high-grade (large cell) lymphoma is a significant prognostic indicator.
Treatment Strategies and Expected Outcomes
Chemotherapy is the primary treatment for nearly all forms of T-cell lymphoma, as the disease is considered systemic even when localized. The specific protocol is tailored based on the tumor’s anatomical location and cellular grade.
High-grade, aggressive lymphomas, such as the mediastinal form, are typically treated with multi-agent protocols like the CHOP regimen. This combines multiple chemotherapy drugs, including cyclophosphamide, doxorubicin, vincristine, and prednisolone. The goal is to achieve remission, meaning a significant reduction or complete disappearance of the tumor.
While chemotherapy is not curative, a significant percentage of cats respond well, with response rates often exceeding 60%. Treatment for the more indolent, low-grade T-cell gastrointestinal lymphoma is less aggressive, often involving only oral chemotherapy with chlorambucil and the corticosteroid prednisolone.
Supportive care is integrated into all treatment plans to maintain the cat’s quality of life and manage potential side effects. Corticosteroids directly shrink some tumors and improve appetite. Cats with the gastrointestinal form often require Vitamin B12 (cobalamin) supplementation. For localized disease, such as nasal lymphoma, radiation therapy is highly effective, sometimes combined with systemic chemotherapy.
The prognosis varies widely based on the T-cell phenotype and location. Cats with the low-grade GI lymphoma generally have the best outlook, with median survival times often ranging from 1.5 to 2 years. Conversely, cats diagnosed with the aggressive mediastinal form (especially if FeLV-positive) have a much shorter life expectancy, often only two to three months. For high-grade forms, median survival times with multi-agent chemotherapy are typically six to nine months.