A cyst is an abnormal, closed sac-like structure within a tissue that contains a liquid,
gaseous, or semisolid substance. A cyst can occur anywhere in the body and can vary in size. The outer, or capsular, portion of a cyst is termed the cyst wall.
Tumor: A swelling of a part of the body, generally without inflammation, caused by an abnormal growth of tissue, whether benign or malignant.
They are different.