While I fully understand your urgent need to have something you feel does not belong on your chest, removed, I can feel for your mother too. 
Any surgery has it's hazards and the thought of that is probably scaring her a lot. Especially if there have been any problems with friends or family's ops.

We are talking elective surgery here though, not some backyard operation in a tribal village.  Have any of your relatives had a face lift? If so, did your Mum think that was 'mutilation?'  It is really just a lot more of the same in a way.
Hope it works out.

I think Evan's comment holds a lot of weight. No matter what we do we will upset our parents in some way. The girl who has implants probably horrifies her Mum 'Why do you want to mutilate yourself'?
The same cry is no doubt heard when children get piercings, tats, none parental hair styles, non-parental clothing etc. OK having surgery may be seen as another level, I remember my Mum horrified when I tried to castrate myself, 'But you won't be able to marry and sire children ,' 

We just have to do what we do because none TG people will never understand. How could they? It is the total reverse of their entire biology and self belief. Why can't we accept how we are? For exactly the same reason.

Cindy

On the empathy angle.

Yes you need to be a little tolerant of your mother. She is growing up as well. Coming to terms with the reality that her little girl won't be a princess, swooped away by Prince Charming.

We all need to grow up. We all need to be tolerant when others are growing up. But it's about accepting the realities of life. Our parents seem to rock solid when we are young. It can be as difficult for us to accept that they are growing up as much as it is for them, that we are independent and think for ourselves.

My mum thought it was 'mutilation' for a long time and gave me a few lectures about 'why do you hate yourself so much that you feel the need to mutilate yourself!?' My eventual reply? 'Mutilation isn't getting the surgery with a proper doctor. That's corrective surgery. Mutilation would be me taking that scalpel in my room to my chest and cutting the lumps off myself.'

She pretty much stopped calling it 'mutilation' to my face after that... Not sure if she still thinks that inside her head or not though. But I think she's accepted that it's something that I really need to do, regardless of whether or not it's 'mutilation'.

You can always find this guy 6pac (6pak? 6pack? don't know the spelling). I know he has surgery pictures on transbucket or another surgery site and he's on youtube (often topless). He has little visible scarring from his surgery.