Cancerous Growth (Fallout Supplement)
From D&D Wiki
You have mutated so badly that you can even regenerate health.
Benefit: You gain Fast Healing 2 and may reattach severed limbs or digits but not your head, sorry dead is dead. In order to reattach a severed appendage you must hold it in place until the damage done that severed it is healed by your Fast Healing. You may not take this feat more than once.
Normal: See Healing