Giant cell tumor of tendon sheath is -

It is also known as giant-cell synovioma and localized nodular tenosynovitis. They are the second most common benign tumor of the hand. They most commonly occur in patients aged 30-50 years. They are associated with degenerative joint disease. Typically, these masses occur along the volar aspect of the hand and fingers and are most commonly adjacent to the DIP joint. Surgery to remove the tumor is a common treatment, though the tumor may recur.