Modification or Mutilation?

How do we separate body modification from body mutilation?

The online encyclopedia defines each word as:

Mutilation or maiming is an act or physical injury that degrades the appearance or function of the (human) body, usually without causing death.

Body modification (or body alteration) is the permanent or semi-permanent deliberate altering of the human body for non-medical reasons, such as: sexual enhancement; a rite of passage; aesthetic reasons; denoting affiliation, trust and loyalty; religious reasons; mystical affiliations; shock value; and self-expression.

It seems to be if the act is done on purpose, it seems to be classified as body modification. If something happens is negative, then it is mutilation? I was hoping to find definitions of both that were not based on the perspective of someone else. It seems like it would be too easy for an act to ride the fence between both adjectives. For example, circumcision has been seen as both, new parents are wishing to have their son circumcised, and as mutilation (perhaps from an adult male who is not circumcised).

What about a surgical procedure that can have both positive and negative side effects? Something that could completely totally ultimately change my life if it worked... or kill me if it doesn't? Cound this be a form of genocide, since the procedure is focused on only one group of people? Hmm that may be a topic later on.