Sentence:  Microscopic studies of the gastrocnemius , pectoralis major , transversus abdominis , biceps brachii , and diaphragm showed atrophy as well as varying degrees of injury ranging from swelling and <WSD>vacuolization</WSD> to focal necrosis of the muscle fibers . 
Meaning of the word marked with <WSD> tags:  the state of having become filled with vacuoles