In his upcoming memoir, Jared Kushner writes that he was treated for thyroid cancer while serving as then-President Donald Trump’s senior advisor, the New York Times reports.

Kushner, Trump’s son-in-law, makes the revelation in Breaking History: A White House Memoir, which is scheduled for publication by Broadside Books next month. The HarperCollins imprint says the book “provides the most honest, nuanced, and definitive understanding of a presidency that will be studied for generations.”

Kushner writes in the book that he learned of his diagnosis from White House doctor Sean Conley while the two were traveling to Texas on Air Force One in 2019.

“Please don’t tell anyone—especially my wife [Ivanka Trump] or my father-in-law,” Kushner told the physician.

Kushner writes that he was told he would need surgery to remove part of his thyroid, and opted to schedule it close to Thanksgiving, when “my absence might even go unnoticed.”

He says that he only revealed his diagnosis to a handful of White House staffers, and did not tell Donald Trump about his illness.

But Trump found out, asking Kushner whether he was nervous about his surgery. When Kushner asked Trump how he knew about it, he says that the then-president responded, “I’m the president. I know everything.…Don’t worry about anything with work. We have everything covered here.”

Breaking History is slated for publication on Aug. 23.

Michael Schaub, a journalist and regular contributor to NPR, lives near Austin, Texas.