Official, not yet
There is a third-party class "The Grafter", although I haven't tried it myself and can't really assess it:
Did you ever get jealous of those sweet abilities monsters have? This is no longer an issue! With the Grafter class you can slowly but surely become a monstrous abomination yourself with all the sweet perks it brings! This is a class for those who like to hunt down monsters for their parts and then use those parts in battle!
The grafter class includes three archetypes: the monster, the symbiont and the witch.
Besides...
There are a couple of related spells and magic items:
- The necromancy "Graft" spell allows you to attach a dead limb.
- The infamous Eye of Vecna and Hand of Vecna from the DMG attaches instead of your own eye or hand