Fox News host Rachel Campos-Duffy expressed doubt about Kate Middleton's cancer because she still has "luscious" hair.

"You know, one thing, just as a layperson," Campos-Duffy told Dr. Mark Siegel on Sunday. "I'm not a doctor like you, Dr. Siegel, but, you know, she said that she's undergoing some preventative chemotherapy."

"I'm gonna, maybe I'm showing my ignorance, but I saw her luscious, you know, full hair, and I thought, well, that's not what I think about when I think about chemotherapy," she insisted.

"So there's two points there," Siegel replied. "First is people should know that preventive chemotherapy is often done when you get it all out."

"Now, you mentioned her hair," the doctor said. "There's two different types of chemo."

"If she had a GYN cancer, she'd probably be on Taxol, which causes you to lose your hair," Siegel added. "That doesn't cause you to lose your hair. So that's where a lot of the debate is coming."

"It seems that it looks like she has her hair. So that would be implying more, again, a GI type of cancer. Taxol does cause you to lose your hair. Then you would be wearing a wig."

Siegel pointed out that it was "something that it's up to her to disclose."