Can my Existing Implant Behind the Muscle Be Left in with a Mastectomy?

First of all I'm sorry for you certain anxiety waiting for your results. Without knowing the specifics of you breast size and implant size I can't comment with confidence. Oridinarilly in this situation, the implant would be removed at the time of mastectomy along with the scar tissue (capsule) around the implant. The tricky part here is that the muscle is very thin and attenuated. As a result it is hard to use for the reconstruction. In most cases, I put in an expander at the time of mastectomy and replace it later with an implant. The advantage here is that I can put in the exact amount of fluid necessary to get the volume I need and the patient can have input as to their desired shape. I wish you the best!

While there are a number of individual factors to consider, it is generally not a good idea to have radiation therapy with breast implants so the mastectomy is often the best option. Often the mastectomy can be done with a skin-sparing technique, and the reconstruction done at the same time. The new implant would need to be larger to compensate for the breast tissue that was removed, and the use of Alloderm to support the implant is also routine, since the muscle only covers the upper portion of the implant.

I am sorry to hear of your recent findings and hope for the best for you.  While it is possible that your implants may remain following your mastectomy, if required, it may not be the wisest decision for you.  Without knowing your current breast size or evaluating you, it is difficult to answer your question accurately.  However, if during the procedure, the capsule or muscle covering your implant is violated, it may certainly introduce an infection around your implant.  Another thing to consider is that you will lose some size from the mastectomy alone.  Immediate implant reconstruction would be ideal for you since you have an already formed pocket.  

Exchanging your current implant(s) for larger size, simply to make up the difference after removal of the overlying breast tissue, would be an excellent option in cases like yours.  Consult with a plastic surgeon for examination and to assist you in determining which procedure, if any, is the right option for you.  Best of luck!