Intramuscular myxoma is a rare, benign tumor of soft tissue that usually appears in the arms, legs, or trunk of the body. It is characterized by a lump or mass that is composed of a jelly-like material. The tumor is usually found deep within a muscle and can cause pain and discomfort, as well as other symptoms. The exact cause of intramuscular myxoma is not known, but it is believed to be related to genetic factors. Treatment usually involves the removal of the tumor through surgery, although radiation therapy may also be used in some cases.