Can cellulitis turn into gangrene?

Could.: Both are infections. In cellulitis the tissues are injured but "not dead yet." Gangrene implies that the tissues have died. Gangrene can be wet or dry or even gas gangrene. Sometimes cellulitis and gangrene co-exist with a central area of gangrene and surrounding cellulitis. In any case dead tissue must be removed surgically.

Very unusual!: Cellulitis, in general, responds to antibiotics and will not lead to gangrene. Gangrene rare unless there's a significant additional problem, like poor circulation, a very nasty untreated infection, significant injury, or some type of poisoning of the tissues. Poor circulation is the most common. 26 would be terribly young to see this. Obviously see Dr. if worried. Hope this helps.