Vanessa Trump, the former wife of Donald Trump Jr, the US president's eldest son, was diagnosed with breast cancer, she said in a social media post.

"While this isn't news anyone expects, I'm working closely with my medical team on a treatment plan," she wrote on Instagram on Wednesday.

Vanessa Trump said she underwent a medical procedure earlier this week and asked the public for privacy while she focuses on her health and recovery.

She separated from Donald Trump Jr, with whom she has five children, in 2018. Vanessa Trump and US pro golfer Tiger Woods announced they were dating last year.

"I am staying focused and hopeful while surrounded by the love and support of my family, my kids, and those closest to me. Thank you for your kindness and support it truly means more than I can express," Vanessa Trump said.

Her social media post received hundreds of messages of support, including from Ivanka Trump, the president's eldest daughter.

"Praying for your continued strength and a swift recovery. Love you mama," she wrote on Vanessa Trump's post.

Vanessa Trump, a former model, was introduced to her former husband by the now-president in the early 2000s.

"I'm at this fashion show," Vanessa Trump told the New York Times in 2006 about meeting Donald Trump Jr. "Donald Trump comes up to me with his son: 'Hi, I'm Donald Trump. I wanted to introduce you to my son Donald Trump Jr.'"

The couple went on to wed in 2005 at Mar-a-Lago, the president's Florida estate.

Now divorced, they share five children who range in age from 11 to 19. Their 19-year-old daughter, Kai Trump, has a large social-media following and has been frequently spotted at the White House with her grandfather.

According to the American Cancer Society, the average risk of a woman in the US developing breast cancer is about 1 in 8, or 13%. The disease also accounts for 30% of all new female cancers every year, according to the group.

Surgery cures most breast cancers, but if some disease remains, chemotherapy, radiotherapy and endocrine therapy can reduce the long-term risk of dying.

Treatments have been advancing, including more targeted therapies for early breast cancer, new types of hormonal therapies, and more precise and effective radiotherapy.