The Cancer Society of New Zealand says today's announcement by the Princess of Wales is a reminder for everyone to look after their health.

Chief executive Rachael Hart said her thoughts are with Princess Catherine and the Royal Family, following her announcement that she is undergoing chemotherapy.

In a video statement, the Princess explained that when she had abdominal surgery in January, it was not known that there was any cancer.

The princess, 42, said she was thinking of all those who have been affected by cancer.

Rachael Hart said that, most of the time people are not thinking about cancer, but if someone they know - or a famous person - is diagnosed, it's a wake-up call.

"This type of announcement is a reminder for all of us to look after our own health.

"If you have unexplained bleeding, or a new lump, or unexplained tiredness or a change in body weight, or anything that's just not right, to go and see your doctor. Go and get it checked out, because you just never know."

Hart said it was also worthwhile seeing a doctor if there's a family history of cancer.

"Make sure you take part in your screening programmes, and know your own normal, your breasts, your skin, so you can find those things early."

The Cancer Society New Zealand said it makes sense that the Princess of Wales's cancer diagnosis was kept out of the public eye until she and her family were ready.

Catherine has said in a video statement that she is undergoing chemotherapy.

The Princess also explained that when she had abdominal surgery in January, it was not known that there was any cancer.

Before her announcement of her cancer diagnoses, the Princess was subjected to intense speculation due to not being in the public eye since her surgery.

A Mother's Day photo featuring her and her three children was found to be edited, prompting several photo agencies to issue "kill notices" which only added fuel to the conspiracy theories of her whereabouts.

Hart said it made sense that the Princess of Wales's diagnosis was kept out of the public eye until she and her family were ready.

"It was Kate's right to keep it quiet and it was good to give her children space to process the news. But I also applaud the Princess for speaking out now, so people can learn."

She said it is difficult for parents going through cancer to choose the right time but it is best to tell children as early as possible, as they know when something is wrong.

Cancer Research UK says that nearly one in two people will develop cancer during their lifetimes, while many more are affected when someone they love is diagnosed with cancer.

Cancer survival worldwide has doubled in the last 50 years.

Hart said hearing about other people's diagnoses can also bring up feelings for those affected by cancer, and they can call their local Cancer Society branch on 0800 CANCER if they want to speak to someone.

This story was originally posted on RNZ News