She was appearing in her regular slot as a host of CBS programme The Talk, when the other presenters asked about her son's diagnosis.
The 59-year-old, who has herself battled cancer, struggled to get her words out as she welled up.
'He's great – he's doing really, really good and I want to thank everyone for all their texts and goodwill and love they send to us," she finally managed to say.
Fellow presenter Julie Chen told Sharon that Jack is "an amazing guy, he's very courageous" before asking: "What else do you want say Mrs O?"
Sharon replied: "Just thank you to everyone for all their good wishes. It's been amazing … for Jack 'cause I really believe that vibes and prayer help."
She added: "And what I'm doing right now is not helping because I'm just feeling sorry for myself, and that is no good.
"So we just have to think positively."
Twenty-six-year-old Jack, who has just welcomed baby Pearl with his fiancée Lisa Stelly, told HELLO! magazine: "The timing was so bad.
"I'd just had a baby, work was going great… I kept thinking: 'Why now?'"
The TV star says it's been a tough few weeks since his diagnosis was officially confirmed last month. But with Lisa's help he is maintaining a positive outlook.
"While I was waiting for the final results, I got really, really angry. Then I got really sad for about two days, and after that I realised: 'Being angry and upset is not going to do anything at this point, if anything it's only going to make it worse… 'adapt and overcome' is my new motto".
Read the full exclusive story on Jack's diagnosis, the medical prognosis, his wedding plans, and how the showbiz world's most famous family plan to rally round Jack, only in HELLO!, on sale now.