Former President Donald Trump’s son-in-law Jared Kushner privately battled thyroid cancer while serving as a White House adviser during the Trump administration, Fox News confirmed.

Kushner, who is now 41, and served as a senior advisor to Trump, learned he likely had thyroid cancer in October 2019 during high-level trade talks with China, but was private about his diagnosis. 

"As this high-wire act of trade talks with the Chinese progressed, I had to confront an unexpected and frightening personal problem," Kushner writes in his new book, "Breaking History: A White House Memoir."

Jared Kushner speaking at the White House

Senior adviser Jared Kushner speaks at a press briefing at the White House in Washington on Aug. 13, 2020. (AP Photo/Andrew Harnik, File)

Kushner writes that he only told his wife, Ivanka Trump, and a small circle, including his aides Avi Berkowitz and Cassidy Luna and then-chief of staff Mick Mulvaney about his diagnosis.

IVANKA TRUMP ‘FOCUSING ON FAMILY TIME’ IN MONTHS AFTER TRUMP ADMINISTRATION

"With the exception of Ivanka, Avi, Cassidy, and Mulvaney, I didn’t tell anyone at the White House — including the president," Kushner writes.

Kushner writes that before a scheduled surgery, Trump ultimately found out.

"The day before the surgery, Trump called me into the Oval Office and motioned for his team to close the door. ‘Are you nervous about the surgery?’ he asked," Kushner writes, noting that he asked then-President Trump "how" he knew.

"‘I’m the president,'" Trump said, according to Kushner. "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."

Ivanka Trump, right, and her husband Jared Kushner, senior advisor of President Donald Trump arrive to the military airport in Warsaw, Poland

Jared Kushner and his wife, Ivanka Trump, arrive in Warsaw, Poland, July 5, 2017. (Associated Press)

JARED KUSHNER LAUNCHES GROUP TO PROMOTE RELATIONS BETWEEN ARAB STATES AND ISRAEL

Kushner ultimately had a "substantial" part of his thyroid removed during an operation.

"The biopsy results arrived a few days later, revealing that the nodule indeed was cancerous. Thank God we caught it early," Kushner writes.

FILE - In this Monday, Jan. 23, 2017, file photo, White House Senior Adviser Jared Kushner, right, listens to President Donald Trump speak during a breakfast with business leaders in the Roosevelt Room of the White House in Washington. Trump is set to announce a new White House office run by his son-in-law, Kushner, that will seek to overhaul government functions using ideas from the business sector. (AP Photo/Pablo Martinez Monsivais, File)

Jared Kushner, the son-in-law of President Donald Trump and top White House adviser, was seeking a private communications channel with the Kremlin, a new report says. (AP)

Fox News first reported last year that Kushner was working on a book.

Since his time in the White House, he and Ivanka Trump have been focused on "family time," a source familiar told Fox News, and have moved to Florida.

Kushner has also started The Abraham Accords Peace Institute, a nonprofit, after working in the Trump administration on the Abraham Accords, which officials touted as a "historic peace agreement" between Israel and the United Arab Emirates that normalized relations and created bilateral agreements regarding "investment, tourism, direct flights, security, telecommunications, technology, energy, health care, culture, the environment, the establishment of reciprocal embassies, and other areas of mutual benefit."

"Breaking History: A White House Memoir" is expected to be available to the public Aug. 23.