The Princess of Wales shared a pic at London’s Royal Marsden Hospital, revealing her new role as the institution's Joint Patron to support their medical research and help transform the lives of those impacted by cancer.

Kate also made a rare visit to the hospital, where she spoke with cancer patients about their health journeys -- something she knows all too well.

The royal also made time for the hospital's staffers, who she thanked for their service, especially after her own battle with cancer.

The princess indicated she was even ready to open up further about her health struggle ... noting it was "nice" to use the front door of the hospital after "having made so many quiet, private visits."

While the British royal was once known for her many public appearances and charitable work, she notably took a large step back last year during her health crisis ... later revealing she underwent chemotherapy to combat a cancer diagnosis.

She's never shared the type of cancer she overcame.

Princess Kate confirmed she had reached the end of her chemotherapy treatment in September, however ... and has slowly but surely returned to the spotlight in the last several months.