The 41-year-old singer has revealed the news in a long note on Facebook, writing that he and his actress wife are completely shattered.
"We are devastated about the recent cancer diagnosis of our oldest son Noah, who is currently undergoing treatment in the US. We have always been very vocal about the importance of family and the love we have for our children," he wrote.
The message goes on to say that Buble and Lopilato will be taking a break from the entertainment industry to ensure the well-being of their child.
"At this difficult time, we ask only for your prayers and respect for our privacy. We have a long journey in front of us and hope that with the support of family, friends and fans around the world, we will win this battle, God willing," he wrote.
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