I have had this happen before but would like the comfort of those with similar experience. I have read about, and experienced, the the fact that Italian bees will sometimes make a queen cell or two in a hive that has a good performing queen. I went into one of my hives the other day and there was a QC toward the top half of the frame with a healthy looking queen larvae capped off inside it. As I mentioned I've had this happen before and have read that Italian bees will do this yet normally destroy the cell themselves. The queen in this hive is a 2010 and is laying wall to wall brood frames-as good as any queen I've had. I am still worried however and destroyed the cell myself. I would have done a split with it but I have some grafted queens in mating boxes and they are all I can use.