Lymphosarcoma

Lymphosarcoma, commonly called lymphoma, is a malignant neoplasm of lymphocytes arising in the lymphoid system. It most often involves lymph nodes but can spread to the spleen, bone marrow, and extranodal sites such as the gastrointestinal tract, nasal passages, skin, or brain. The term is historical; in veterinary medicine it is used for canine lymphoid cancers and is classified by site and histologic grade.

Subtypes and presentation: The classic form is multicentric lymphoma, presenting with enlarged peripheral lymph nodes. Other forms include mediastinal, alimentary (gastrointestinal), nasal, and various extranodal lymphomas. In dogs, B-cell lymphomas predominate; T-cell lymphomas occur less frequently and are often associated with a poorer prognosis. In cats, lymphoma is linked to FeLV infection in several subtypes.

Clinical signs and assessment: Signs depend on the affected site and may include rapidly enlarging lymph nodes, weight loss, reduced appetite, lethargy, vomiting or diarrhea, abdominal distension, coughing, or nasal discharge. Blood tests may show anemia or abnormal lymphocytes; imaging and tissue sampling are used to confirm diagnosis and assess extent.

Diagnosis and staging: Diagnosis is usually by cytology or biopsy of involved tissue, with immunophenotyping to differentiate B-cell from T-cell lymphoma. Staging uses a system that ranges from I to IV based on nodal and organ involvement, with a separate designation for clinical signs. Additional tests may include ultrasound, radiography, and bone marrow evaluation.

Treatment and prognosis: Many lymphomas respond to chemotherapy, with CHOP-type protocols commonly used for canine multicentric lymphoma; radiation therapy may be employed for localized disease. Prognosis varies by species, subtype, stage, and treatment response; median survival in dogs typically ranges from months to a year or more in favorable cases, with shorter outcomes for high-grade or FeLV-associated disease.