The spleen is an important part of the lymph system and it functions as drainage that helps the body fight infections and diseases. It sits below the rib cage in the upper left part of the abdomen region. White and red blood cell regulation is a function of the spleen and any abnormal blood cells that are in the bloodstream is distilled by the spleen. There are various reasons the spleen can become enlarged and some of these include:
Some cancers can affect the spleen and cause it to become larger in size. Leukemia  and lymphoma both affect the spleen differently but cause it to enlarge. In Leukemia, there is an overproduction of white blood cells which invade and attack the spleen causing it to become enlarged. Lymphoma is a cancer of the lymph tissue which causes the spleen to become enlarged. Other cancers could also spread in their later stages and cause complications to the spleen leaving it enlarged. Although other cancers can cause the enlarging of the spleen, it is not a common occurrence except the spleen is attacked directly.