Does this look like necrosis? Sclerotherapy done a week and 4 days ago. What is the grey in the middle? Will it spread? (Photo)

It's a little hard to tell from the photos but it doesn't look like true skin necrosis.  However, there are other side effects of sclerotherapy (hyperpigmentation, matting, etc) most of which will resolve on their own over time. 

The posted pictures do not look like necrosis but rather like bruising and staining following sclerotherapy.  It is only a short time from your treatment and you need to give it more time to heal.  The dark areas may require draining with a small needle.  Wearing compression, applying Dermaka cream and avoiding sun exposure will also help.

This does not look like skin necrosis, but more consistent with bruising and possible hyperpigmentation known as staining.  I would see you treating physician to have it evaluated.Sometimes in the first 1-2 weeks trapped blood can form, almost like a blood blister.  Draining this can speed up the healing and reduce chances of staining.  I also recommend Arnica gel - OTC- to help with the bruising.Last, as long as it is dark, avoid direct sun exposure as this can make it worse and/ or permanent.Good luck to you,Dr. Powell