'Why my mummy?': Heartbreaking video shows boy reading mum's book to help him understand cancer

Krystal Johnson

A Queensland mother has posted a heartbreaking video showing her nine-year-old son read the book she wrote to explain to him she is dying from cancer.

Donna Penny, 42, was diagnosed with breast cancer at 30 years old and has been battling the disease since 2008, when her son Kai was just one year old.

Donna created a book to explain to her son Kia, why his mummy is sick. Photo: Why My Mummy

She first found a lump in her breast but was given the all clear after the mammogram didn't show any ill signs.

However, the disease returned five years later and she was forced to have a double mastectomy.

The cancer has since spread to her lymph nodes, spine, shoulder and other parts of her body.

This is the beautiful moment Kai reads exerts from his mother's book. Photo: Why My Mummy

The mum was given two years to live, telling the Daily Mail she has lived 'nine months past her expiry date'.

When the Sunshine Coast mother was first diagnosed, she struggled to find a book that could explain to her son what was happening to his mum.

"I couldn't find a single book to read to Kai about cancer," she wrote on her website.

"How do you explain to a child what terminal means? Why your hair is falling out? How can I help my son to process the fear of loosing me?"

Kai was only one when his mother was first diagnosed with cancer. Photo: Why My Mummy

Kai has never known his mother not to be sick.

He asked his dad Jason on the drive to school: "Why my mummy?".

The brave mother decided she would write a book from his perspective about her experience, as a way to explain to him what the disease is doing to her body and that it is never going away.

Donna was forced to have a double mastectomy and has already fought 9 months past her

Donna has since written Why My Mummy , filming the heartbreaking moment Kai reads through it.

"The medicine they give my mummy has also made her hair fall out, she has a beautiful soft head that I like to kiss and touch," Kai says.

"She has lots of hats and scarves and sometimes wigs."

Donna first felt a lump in her breast in 2008 but was given the all clear after having a mammogram. Photo: Instagram

"The doctors have told my mummy that her cancer will never go away. They just have to keep it asleep with lots of medicine.

The book explains the journey she and her family have been through while going through chemotherapy and what the word "terminal" means.

Donna wrote a book from the perspective of her son about why his mummy is sick. Photo: Instagram

"My mummy has to spend a lot of time in hospital, but she always comes home.

"I love you mummy."

Donna is pictured with her husband, Jason. Photo: Instagram

Donna believes it has helped Kai understand what is happening to her without mentioning death.

The mum is seeking donations through a crowd-funding website to get her book published and plans to donate copies to hospitals, schools and libraries.