Is there any need to remove pectoral muscle during prophylactic mastectomy?

Muscle is typically not removed during the mastectomy portion of the procedure.  However, findings during the procedure may have required this to be done.  Given that you underwent DTI breast reconstruction, it is likely that your previous surgeon had disinserted the muscle to allow for the implant to be placed in the subpectoral position.  S/he may have replaced this portion with a dermal matrix to provide complete coverage of the implant.  The muscle had likely "window-shaded" superiorly, and may appear that muscle was removed.  Regardless, communication amongst your surgeons would be needed to determine that.  

Thank you very much for your enquiry.Normally a prophylactic mastectomy the
pectoralis major muscle is retained as it is the breast tissue itself not the
muscle which is removed.Some people do have a very small pectoralis
muscle normally but if you would like further information about the original
state of your pectoralis major it might be worthwhile asking your orginal
surgeon the details of the operation and perhaps obtaining a copy of the
operation note which should detail exactly what was performed during the
operation.I hope your DIEP goes well and wish you
the best of luck in the future.AR

pectoralis muscles not usually removed with a prophylactic mastectomy.   I think he should have your present plastic surgeon speak directly with your previous surgeon to see exactly what was done.  It would be hard for you to interpret and understand, let the experts figured out

The muscle should not be removed with a prophylactic mastectomy.  You should ask your surgeon why or if this was done. When an implant is placed, the implant will be placed under the muscle, so that it can be adherent to the upper flap.