Is this necrosis? (photos)

From your pictures, it does appear that the blood supply to a portion of your mastectomy flap is inadequate and this has led to some necrosis of the mastectomy skin flap. Sometimes, wounds such as this can heal with local wound care as they are only partial thickness necrosis. With breast reconstruction on the other hand, there is an implant beneath that area, so one has to be very careful about opening of the wound and exposure of the implant. Some surgeons in this case would favor aggressive management with excision of the necrotic area and repeat wound closure. I would strongly advise you to see your plastic surgeon sooner rather than later and discuss with them the options for treatment that he or she feels are in your best interest. 

Thank you for providing photographs with your question. It's very helpful! Based on the images you do have necrosis of the skin flaps. Please contact your plastic surgeon today to be evaluated sooner rather than later. With an implant based reconstruction you are at an increased risk of developing an underlying infection. I am sorry that you've had so many difficulties with your reconstruction so far. I wish you the best!

Unfortunately based on the picture it does appear to show some level of necrosis of your skin. I would follow up with your surgeon and see what they recommend to do.