Medical Content Created by the Faculty of the
Harvard Medical School
Lymph nodes are small balls of tissue that are part of the body's immune system. The nodes produce and harbor infection-fighting white blood cells (lymphocytes) that attack both infectious agents and cancer cells. Cancer, infection, and some other diseases can change the appearance of lymph nodes. For that reason, your doctor may ask a surgeon to remove lymph nodes, to be examined microscopically for evidence of these problems.
Usually, one or more entire lymph nodes are removed and examined under the microscope by a pathologist. On occasion, the doctor does a needle biopsy to remove a portion of a lymph node to see whether a cancer already diagnosed has spread to that point.