Sources with direct knowledge tell TMZ ... Kate's treatments -- which included chemotherapy -- have gone well over the last 3 months. So well, in fact, that she and the Palace are planning for her to resurface in public ... possibly as soon as this weekend.

The big question for folks in the UK has been, "Where's Kate?" ... as she's rarely been seen since she made the announcement in March that she's battling a form of cancer.

The good news about Kate's health comes just as Buckingham Palace prepares the annual Trooping the Colour ceremony ... a parade to mark the anniversary of the Monarchy.

Everyone's been wondering if Kate would join her husband Prince William, King Charles and the rest of the Royals for the celebration, and the positive update on her health seems to open the door for her to make a triumphant return to public events.

There's been much speculation over the past few weeks over whether Kate would show for this -- as she normally goes to Trooping the Colour, under normal circumstances. She was in attendance in 2023, and has been a consistent presence on the balcony over the years.

If she attends on Saturday, it would mark Kate's first Royal engagement since she's been sidelined, following an abdominal surgery earlier this year ... where cancer was discovered by docs.

As you know ... Kate went public with her diagnosis in March -- this after mounting rumors about her condition as she remained out of the public eye, which were fueled by conspiracy theories and memes.

Once Kate came forward to explain, though, there were a lot of folks who were eating crow -- and many notable people issued apologies in the aftermath ... including Blake Lively.

Kate hasn't been seen in public very much since then -- but she was spotted out and about near her home in Windsor shortly before she released her video message ... walking next to William at a local shop in town, where she appeared to be in relatively good spirits.

She noted in her video message from March that she was undergoing chemotherapy ... and that she'd need time and privacy to attend to her health, and to deal with her own family.