BeastieBoys.com, the band has been forced to cancel the Lollapalooza performance - in addition to all other planned concert dates - because of a cancerous tumor found in singer Adam "MCA" Yauch's left parotid gland.
Fortunately, Yauch said that the cancer was detected early enough that it's expected to be fully treatable with surgery.
"About two months ago I started feeling this little lump in my throat, like if you have swollen glands or a cold. I didn't really think of it as anything," Yauch said in the video. "The good news is that they did scans on my hold body and it's only localized in this one area and it's not in a place that affects my voice. It's a bit of a setback and a pain in the ass, but it's something that's very treatable."
The Beastie Boys were slated to headline the festival on Saturday, August 8. They were also set to play an August 6 show at Congress Theater.
Lollapalooza promoters are expected to comment on the situation later today.