Breast fat? ...and plenty of it.
My biggest issue with what Cyrus did was that it sucked. Bad singing, worse dancing, and even less sex appeal. She looked like a person who doesn't know what sex appeal is but was told about it and is trying to act sexy.
She wasn't sexy the way porn isn't sexy. It's sex but its not sexy. I can't believe whatever show coordinator they have didn't put the kibosh on the whole thing. It just sucked.