The Mickelsons have been married for 13 years
Phil Mickelson has suspended his PGA Tour schedule after his wife was diagnosed with breast cancer.
The 38-year-old was due to play at the Byron Nelson Championship starting on Thursday and defend his title at Colonial next week.
But he has withdrawn to be with his wife Amy, 37, who faces "major surgery, possibly within the next two weeks", according to the PGA Tour website.
The Mickelsons married in 1996 and have three children.
Mickelson is a two-time Masters champion and winner of the 2005 US PGA Championship.
Tiger Woods offered words of sympathy and support on hearing the news.
"Elin and I are deeply saddened to hear the news about Amy. Our thoughts and prayers are with her, Phil, the children and the entire Mickelson family," said Woods.
PGA Tour commissioner Tim Finchem said: "We are saddened by the news of Amy Mickelson's diagnosis, but are hopeful that with the support of Phil and her family and friends, she will come through this difficult time.
"The thoughts and prayers of everyone connected with the PGA Tour are with the Mickelson family."