What is the yellow stuff in my open wound? (Photo)

Thank you for your excellent photographs.  It appears you had a standard breast lift and a minor wound dehiscence (wound separation).The yellow material present at the base of this dehiscence is a combination of breast fat and dried wound exudate (extra cellular fluid with a high protein content mixed with cell debris).  This exudate was released onto the surface of your wound to protect your breast from bacterial invasion.  Every plastic surgeon has his or her own technique for dealing with this type of dehiscence.  If you were my patient, I would recommend a topical antibiotic such as Silver Sulfadiazine cream.  Since it is water based, it will keep this tissue moist and wounds heal best in a sterile, moist environment.  The process of this type of healing is very interesting in that wounds of this nature get smaller with time because of wound scar contraction.  At the same time as there is wound scar contraction, there is also some formation of new epithelium .  You didn't ask, but I feel a necessity to tell you that this type of wound is not terribly unusual and I am sure your plastic surgeon will get you through this minor bump in the road.  What is most interesting here is that there is rarely much of a scar left, even with a wound of this nature.

It's most likely fat underneath the skin that is exposed.  With careful follow up, you should heal well.

Thank you for your question and photographs.  The yellow tissue is exposed fat that was under the skin that was lost.  Your surgeon should instruct you on proper wound care.  Some of this fat will gradually come off, then, as it gets healthier, the tissue will look pink and then almost red.  This is called granulation tissue which has a healthy blood supply which will allow the skin cells to grow over the opening. Be patient, it will probably look worse before it looks better, but it will heal.  Continue to follow up with your plastic surgeon.