The term 'Abnormal Body Sac' can be summarized as a CYST, which is a four-letter word. A CYST is an abnormal sac-like structure that can contain fluid, gas, or semi-solid material. It can form in any part of the body and can be caused by infection, obstruction of a duct, or trauma. Cysts can be benign or malignant, and can cause pain or discomfort depending on their size and location. Treatment for cysts can range from simple observation to surgical removal.