London — Catherine, the Princess of Wales, offered a rare health update Friday, saying in a statement that she is still undergoing chemotherapy for an undisclosed form of cancer and has "a few more months" of treatment left, but that she is making "good progress." Princess Kate, as she's often known, also announced her first formal step back into public life.

The princess said in her statement, which she also posted on social media, that she would attend a massive military parade on Saturday with her family to mark King Charles III's birthday.

Kate was diagnosed with cancer earlier this year and has remained out of the public eye as she undergoes her chemotherapy treatment, which she said in March was "preventative." Without sharing more about her condition, her office had said she would not return to her public duties until she was cleared by her medical team.  

She has been seen once, visiting a farm shop with her husband in early March, several weeks before she announced her diagnosis, but Saturday will be her first formal public appearance since she was hospitalized for abdominal surgery in January. It was during that procedure that the cancer was detected.

Kate said in her Friday statement that she was "not out of the woods yet," and that she had been "been blown away by all the kind messages of support and encouragement over the last couple of months. It really has made the world of difference to William and me and has helped us both through some of the harder times."

Kensington Palace released a new photo of Kate in conjunction with her statement on Friday, which it said was taken earlier in the week at the royal family's Windsor estate west of London. 

"I am making good progress, but as anyone going through chemotherapy will know, there are good days and bad days. On those bad days you feel weak, tired and you have to give in to your body resting. But on the good days, when you feel stronger, you want to make the most of feeling well," she said.

Kate said she had been doing some work from home, and it's understood that she will start taking on a bit more on the days she's feeling well enough to do so.  

Kate did not attend the Colonel's Review last Saturday, a formal dress rehearsal for the annual Trooping the Colour parade that marks the official birthday of the British monarch. Trooping the Colour is a tradition that dates back to the 18th century, and it does not coincide with the monarch's actual date of birth, which for 75-year-old Charles is in November.

Kate is the honorary colonel of the Irish Guards, and the military unit shared a letter on social media in late May in which the princess sent her apologies in advance for missing the parade rehearsal.

"Being your colonel remains a great honor and I am very sorry that I'm unable to take the salute at this year's Colonel's Review," Kate wrote in the letter. "Please pass my apologies to the whole regiment, however I do hope that I am able to represent you all once again very soon."

Kate's father-in-law, King Charles III, was also diagnosed with an unspecified cancer earlier this year and has been undergoing treatment. He has eased back into his public duties and said he will attend the Trooping of the Color parade, though he said he would ride in a carriage rather than on horseback for the procession.

In:
• British Royal Family
• Prince William Duke of Cambridge
• Kate Middleton
• United Kingdom
• Catherine Princess of Wales

Haley Ott

Haley Ott is the CBS News Digital international reporter, based in the CBS News London bureau.

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