Michael Flatley, best known as one of the creative forces behind Riverdance, has been diagnosed with an “aggressive” form of cancer, according to a social media update. A post on the 64-year-old’s Instagram account said on Wednesday that Flatley had “undergone surgery and is in the care of an excellent team of doctors.” No further details were offered, with Flatley’s team asking “only for your prayers and well wishes.” Before retiring in 2016 over injuries, Flatley all but reinvented traditional Irish dance, beginning with a seven-minute intermission show at the 1994 Eurovision Song Contest that catapulted him to fame. That show, Riverdance, became the basis for a full-length theatrical production that debuted in 1996. Flatley went on to produce the Irish dance shows Lord of the Dance, Feet of Flames, and Celtic Tiger Live, which in combination with the original Riverdance have been watched by more to 60 million people around the world. He had a previous encounter with cancer in 2003, when he battled a malignant melanoma which had been spotted by an MTV viewer. “It was purely by chance that it was noticed,” he told the Irish Independent at the time. “[I]t can be a frightening place to be.”