Scattered throughout the body are numerous lymph nodes. The lymph nodes are immune centers that help to fight infection. When your veterinarian examines your pet, multiple lymph nodes will be felt to assess for normal size and texture. Enlarged lymph nodes can be caused by infections (viral, bacterial, and fungal), inflammation, and tumors. If your veterinarian finds an enlarged lymph node, a small sample of the lymph node can be aspirated and evaluated under the microscope. Under the microscope, inflammatory processes can be distinguished from cancer. Occasionally, lymph nodes need to be biopsied if the aspirate sample is not conclusive.