A necrotic lymph node contains tissue that is dead, usually due to an infection that prevents blood from flowing to the tissue, according to MedlinePlus. Although the condition is usually not serious, necrosis is not reversible and the tissue does not regenerate.
Necrosis can be benign or it can indicate lymphoma, which is cancer of the lymph nodes, according to the Free Dictionary. Benign necrosis can result from viral or bacterial infections, such as cat-scratch disease; Epstein-Barr virus; fungal infection; chlamydia; a parasitic disease, such as toxoplasmosis; tuberculosis; trauma; blocked blood vessels; and Kawasaki's or Castleman's disease. Many cases are caused by more than one infectious agent. Patients who test positive for HIV have a higher risk of infection, according to the American Family Physician. Cancer of the lymph nodes can start in the lymph nodes, but more often it originates in other parts of the body and spreads through the lymph system, according to the American Cancer Society.
The lymph network is part of the body's immune system. It collects waste, such as carbon dioxide, bacteria and viruses, and delivers nutrients and white blood cells to the cells. Nodes become swollen while they are filtering infectious organisms, injured cells or cancer from the lymph fluid, the American Cancer Society explains. There are hundreds of lymph nodes throughout the body.