Cyst, Mass or Tumor
Cyst. A cyst is a sac that may be filled with air, fluid or other material. A cyst can form in any part of the body, including bones, organs and soft tissues. Most cysts are noncancerous (benign).
Tumor. A tumor is any abnormal mass of tissue. Like a cyst, a tumor can form in any part of the body. A tumor can be benign or cancerous (malignant).
To determine whether a cyst or tumor is benign or malignant, a sample of the affected tissue or, in some cases, the entire suspicious area is removed and studied under a microscope. This is known as a biopsy.
Mass. A mass is the same as a tumor. A mass, like a tumor, may take any shape and is usually not round.