Lionel Richie & Mariah Carey were supposed to be at PPGPaints Arena next week.. until Lionel had to undergo knee surgery. They've rescheduled, but, according to RollingStone.com:
The new tour launches on July 21st in Oakland, CA and wraps in Seattle on September 5th. As Billboard reports, the 35-date tour has been shortened, with shows cancelled in Pittsburgh, Cleveland, St. Louis, Nashville and Charlotte. Lionel Richie's official website lists 22 rescheduled dates for the tour.
I imagine you can contact Ticketmaster, or the Arena for a refund if you have tickets..