Kate Middleton didn't wear her engagement ring that once belonged to Princess Diana at the Royal Marsden Hospital in London on Jan. 14. Inside why and more about Princess Kate's new ring.

For the treatment, which concluded in September, Kate attended the Royal Marsden Hospital in central London and on Tuesday she paid an official visit there to mark her becoming joint patron of its specialist cancer unit along with her husband Prince William.

The problem is that a complete remission does not mean the cancer is gone. Even when a cancer is “cured” — defined as no evidence of cancer for five years — it may not be vanquished.