(CNN) -- World number two Phil Mickelson has indefinitely suspended his PGA Tour schedule after his wife was diagnosed with breast cancer. 

Phil and Amy Mickelson have been married for 13 years and have three children. 

Three-time major winner Mickelson was due to play at the Byron Nelson Championship starting on Thursday and defend his title at Colonial next week -- but has withdrawn to be alongside his wife, Amy. 

"After undergoing an extensive battery of tests Phil Mickelsons's wife, Amy, has been diagnosed with breast cancer," said a statement on the American's official Web site. 

"More tests are scheduled but the treatment process is expected to begin with major surgery, possibly within the next two weeks." 

Mickelson met his wife, a former cheerleader for the Phoenix Suns National Basketball Association team, in 1992 and they were married in 1996. 

They have three children -- nine-year-old Amanda, seven-year-old Sophia and Evan who is six. 

PGA Tour commissioner Tim Finchem said on the official PGA Web site: "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 tim. 

"The thoughts and prayers of everyone connected with the PGA Tour are with the Mickelson family." 

World number one Tiger Woods added: "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." 


Is she going to have surgery?
"More tests are scheduled but the treatment process is expected to begin with major surgery