An abnormal vesicle is a CYST, which is a closed sac-like structure that contains fluid or other material. It can be found in any part of the body and can be caused by infection, inflammation, trauma, or blockage of a duct. Abnormal vesicles can cause pain, swelling, and other symptoms depending on their location. Treatment for an abnormal vesicle may include draining the CYST, medications, or surgery.