'Lord of The Dance' Michael Flatley Battling Aggressive Form of Cancer

Michael Flatley's battling cancer again ... but this time he says it's an "aggressive form" and he's already gone under the knife.

The "Lord of the Dance" creator revealed his diagnosis Wednesday, saying he's "been diagnosed with an aggressive form of cancer."

Michael also says he's "undergone surgery and is in the care of an excellent team of doctors" ... and now he's asking for prayers and well-wishes.

The "Riverdance" legend has already beaten cancer once ... just last year Michael revealed how he fought skin cancer way back in 2003, crediting a fan for spotting the early signs of malignant melanoma on his body.

Michael's on the record saying his first bout with cancer changed his outlook on life ... he says it made him want to live every moment, gave him more focus on his career, and taught him to value friends and loved ones more than material possessions.