Former President Donald Trump’s son-in-law and top adviser, Jared Kushner, quietly fought thyroid cancer while serving under the president, Kushner revealed in an upcoming memoir.

Kushner’s memoir, “Breaking History: A White House Memoir,” set to be released Aug. 23, details how he had to undergo surgery to remove a tumor in his throat but tried to hide his diagnosis from his father-in-law, the New York Post reported Monday.

Kushner received his diagnosis in October of 2019 while the administration was discussing trade with China, according to the outlet.

“As this high-wire act of trade talks with the Chinese progressed, I had to confront an unexpected and frightening personal problem,” Kushner reportedly wrote. “On the morning that I traveled to Texas to attend the opening of a Louis Vuitton factory, White House physician Sean Conley pulled me into the medical cabin on Air Force One. ‘Your test results came back from Walter Reed,’ he said. ‘It looks like you have cancer. We need to schedule a surgery right away.'”

Kushner said he told his wife, Ivanka, the following morning. (RELATED: Jared Kushner To Open Investment Firm Headquartered In Miami: REPORT)

“With as much confidence as I could conjure, I told [Ivanka] not to be concerned,” Kushner recounted, according to the report. “Whatever this was, we would find a way to work through it. She joined me for the meeting with Dr. Conley, as did [West Wing aide] Avi Berkowitz.”

“Dr. Thomas Fahey of New York-Presbyterian Hospital concluded that I needed surgery to remove an unusual growth in my thyroid, and we scheduled the operation for the Friday before Thanksgiving. That way, I would miss the least amount of time in the office. My absence might even go unnoticed. That’s how I wanted it.”

Kushner reportedly said aside from Ivanka, Avi, then-White House acting chief of staff Mick Mulvaney and Cassidy Luna, no one else at the White House knew — not even Trump.

Kushner said after his diagnosis he felt “guilty” that he had been “absent” from his children’s lives over the preceding years, the NY Post reported.

“Every night, before I went to bed, I lingered for a few extra moments in my children’s rooms. I watched them sleep without a care in the world. I felt guilty that I had been so distracted and absent over the previous few years,” Kushner reportedly wrote. “I was always at work or taking phone calls when they wanted to spend time with their dad. I missed plays and sporting events. I had promised myself that when my service in the White House ended, I’d make up for lost time. Now I was forced to confront that possibility that my time might be up. I prayed that the surgery would be successful.”

Despite his best attempts to keep his diagnosis hidden from Trump, the day before the surgery Kushner said “Trump called [him] into the Oval Office and motioned for his team to close the door. ‘Are you nervous about the surgery?’ he asked.”

“How do you know about it?”

“I’m the president,” Trump reportedly said. “I know everything. I understand that you want to keep these things quiet. I like to keep things like this to myself as well. You’ll be just fine. Don’t worry about anything with work. We have everything covered here.”

A “substantial part” of Kushner’s thyroid was removed during the operation, Kushner wrote, according to the NY Post.