Lymph nodes are small rounded organs scattered throughout the body in the path of lymph circulation. Lymph is a biological fluid containing many cells involved in the defense of the body , including leukocytes or white blood cells. They have a major role in responding to attacks of foreign elements by producing antibodies and releasing them into the bloodstream. Their normal size generally does not exceed one centimeter in diameter, but in some diseases such as infection or cancer, they can increase in volume : it is called lymphadenopathy or adenomegaly . The lymph nodes are sometimes grouped in specific areas of the body in the form of lymph node chains, mainly in the neck. Inflammation of one or a few lymph nodes that are close together leads to suspicion of a local infection; if all nodes are affected , a more general disease may be involved.