Kate, the Princess of Wales, has disclosed that she has cancer and is undergoing chemotherapy — though in a video announcement Friday, she did not say what kind of cancer or reveal details of her treatment.

Here’s what is known:

Kate had what was described as abdominal surgery on Jan. 16. The news wasn’t announced until the next day, when Kensington Palace revealed that Kate was recovering from a planned operation.

At the time, officials said her condition wasn’t cancerous but did not specify what kind of surgery, saying only that it was successful.

During the video announcement Friday, Kate said: “Tests after the operation found cancer had been present,” and that she was in the early stages of treatment.

She didn’t say what kind of cancer was found, nor did she give details of her chemotherapy. The statement from Kensington Palace said Kate found out about the cancer after post-surgery tests were done.

While it’s rare to find cancer after surgery for a noncancerous problem, it does happen in about 4% of such surgeries, said Dr. Yuman Fong, a surgeon at City of Hope cancer center in Southern California.

“That 4% figure represents someone who’s going to the operating room for what is thought to be benign disease” such as a procedure to remove the gallbladder or ovarian cysts, Fong said.

Yes, cancer is rare in young adults. But in developed countries, rates of some cancers are rising among younger adults. Kate is 42.

“We hate it when young people get cancer, but at the same time, they are the ones that recover best,” Fong said.

The palace statement said no details would be provided about her cancer or her treatment, other than she started it in late February.

“We will not be sharing any further private medical information. The Princess has a right to medical privacy as we all do,” the statement said.

After successful surgery, chemotherapy is often used to help kill any stray cancer cells and to prevent the cancer from coming back. Treatments have evolved, and when chemo is used now, it’s sometimes for shorter periods or lower doses than it once was.

Fatigue, nausea, tingling in the hands and feet, and sometimes hair loss are side effects of chemotherapy, said Dr. Monica Avila of Moffitt Cancer Center in Tampa, Florida. But there are medications for improving these side effects. And cold caps that cool the scalp can prevent hair loss, Avila said.

“A patient can take anywhere from a few weeks to a month or two to recover from those effects,” Avila said. Numbness and tingling can take longer to disappear, she said.

The palace statement said that will be up to her doctors. “The princess is now on a recovery pathway,” the statement said.