Joan Rivers is a comedian known to cross the line from time to time with her humor, but the shoe was on the other foot when a CNN interviewer's questions caused 81-year-old Rivers to storm off set.

CNN anchor Fredricka Whitfield kept a smile on during the interview to promote Rivers' new book, "Diary of a Mad Diva." Her questions, on the other hand, didn't quite match her pleasant expression as she challenged Rivers on the controversial nature of her humor. Whitfield specifically called out Rivers' critiques on E! Network's "Fashion Police," saying it could be considered "mean."

"It's not mean, it's not mean, it's not mean. I tell the truth," Rivers said. "I'm sure I say the same things that all the viewers say to their friends sitting next to them on the couch."

Rivers added that she didn't think that celebrities cared all that much.

"These ladies make $28 million a picture," she said. "Do you really think that Nicki Minaj cares I didn't like her dress?"

Whitfield pressed on, pointing out that Rivers often made fun of topics that many would consider "off-limits," such as Princess Diana and Casey Anthony.

"Life is very tough," Rivers said in defense. "If you can make a joke to make something easier and funny, do it."

Rivers' limit was reached when Whitfield mentioned her choice of wardrobe on the book's cover, a fur outfit that could potentially anger animal rights activists.

"This whole interview is becoming a defensive interview," Rivers said. "Are you wearing leather shoes? Then shut up."

Soon after, Rivers stood up to leave, pulling off her earpiece and saying that Whitfield was excessively "negative" and "not the one to interview a person who does humor."

Whitfield claimed to believe that Rivers was joking with her and that it was stunt, but off-camera recordings of Rivers dropping "some rather unflattering four-letter words" proved she was more than serious.

Check out the CNN interview below.

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