Masses That May Mimic Soft Tissue Tumors
Ganglion is a benign cystic mass containing a gelatinous fluid rich in hyaluronic acid and other mucopolysaccharides, with a fibrous capsule without synovial lining (McCarthy and McNally 2004). The mass arises from the joint capsule, ligaments, tendon sheaths, bursae, or subchondral bone (Bermejo et al. 2013). Ganglion is usually found in the periarticular soft tissues in areas under repetitive stress, with or without communication with joint spaces. Occasionally, they can occur far from a joint or even in an intramuscular location. The origin of the fluid has been postulated to arise from one of following three mechanisms. First, it may be pumped into the cyst from the joint by motion of the wrist. Second, it may result from an extra-articular degenerative process, cyst formation, and subsequent communication with the joint. Lastly, it may be the result of excessive mucin production by mesenchymal cells within the wall (Gude and Morelli 2008). Intraneural ganglion cysts are rarely found. The common peroneal nerve is most frequently involved, and other affected nerves are often located near articular spaces. The cystic lesion is located within the epineurium, causing an eccentric displacement of the nerve fascicles. The proposed pathogenesis of intraneural ganglion cyst is a dissection of synovial joint fluid into the epineurium of an articular branch nerve supplying a joint, with subsequent centripetal dissection into the parent nerve (Spinner et al. 2007a, b).