Michael Buble's wife Luisana Lopilato discovered their son had cancer after refusing to accept a doctor's initial diagnosis of mumps.
Luisana, 30, was filming in her native Argentina when Noah became sick last year but the three-year-old's usual pediatrician was not in the country.
She was told it was likely he had the viral infection but insisted on getting a second opinion from her family doctor when he arrived, who told her Noah's illness was unlikely to be mumps.
"I had been told that he had mumps, a swollen gland," she told Argentine TV presenter Susana Gimenez. "His pediatrician just was not in Argentina. When his doctor arrived, he told me that this did not look like mumps."
The medic advised that Noah should take further tests, and after an ultrasound scan revealed he might have a tumor, she flew with her son to the U.S where he was formally diagnosed with cancer.
She added, "If I hadn't done the ultrasound to rule out mononucleosis (glandular fever), they (Noah's doctors) wouldn't have discovered what they did in his stomach and it would have been worse after."
The actress flew to America without her crooner husband, who was working in the U.K. as she couldn't get hold of him. But the couple had agreed that if their children became sick they would be treated in Los Angeles as the city is equidistant from their families' homes in Argentina and Canada.
"Mike wasn't with me at the time," she revealed. "He was just about to do a very important interview in England and I couldn't get hold of him on the phone so the day I found out Noah had something in his stomach and the doctors didn't really know what it was and whether it might be a tumour, I got a flight to the States."
When she relayed the news to Michael he immediately canceled his touring and presenting commitments and flew to be by his wife and Noah's side. Happily, eight months later the toddler is now recovered having finished his cancer treatment.
In the emotional interview broadcast on Argentina's Todo Noticias channel, the actress thanked God that their eldest son had recovered.
It has been reported that Noah was treated for liver cancer, but Michael and Luisana have never confirmed the type of cancer he suffered from.