Coloured X-ray (front view) of the abdomen of a 35 year old patient, showing a calcified cyst in the spleen (at upper right). A cyst is a lump or sac filled with fluid or semi-solid material that may occur in any organ or tissue, and if it is large it may disrupt the function of the organ. The spleen is a source of red blood cells and a cyst in the spleen may result in anaemia.