Canine lymphoma is a type of cancer that affects the lymphatic system in dogs. It occurs when lymphocytes, a type of white blood cell, grow uncontrollably. This disease can manifest in various forms, with the most common being multicentric lymphoma, which affects multiple lymph nodes throughout the body. Symptoms of canine lymphoma may include swollen lymph nodes, weight loss, decreased appetite, and lethargy. Diagnosis typically involves a physical examination, blood tests, and a biopsy of affected tissues. Treatment options often include chemotherapy and, in some cases, radiation therapy, aiming to improve the dog's quality of life and extend survival.