Canker being dead tissue, correct?
It looks like a gall which has turned into a large burl to me. This may be caused by many biotic or abiotic agents. The tissue is still alive. Stig would probably kick someones eyeball out for that if the tree were ever to be removed. Valuable for turners, gunstocks and other woodworking uses.
Nothing to worry about, looks funky but structurally sound, perhaps even to the point of creating greater integrity.