Rising British star David Horsey has claimed an early share of the clubhouse lead in the BMW PGA Championship, and then revealed how he could empathise with American star Phil Mickelson, who has withdrawn from golf following confirmation that his wife, Amy, has breast cancer.

Horsey, 24 and a Walker Cup winner, wore a pink wrist band on behalf of breast cancer charities while carding a five-under-par opening round of 67 at Wentworth because his mother, Anne, is also fighting the disease.

"My mum was diagnosed last year," he said. "She had her first chemo treatment yesterday and I think she's got three weeks of radiotherapy coming up. Hopefully, she'll recover and be feeling well by the end of the year."

Amy Mickelson's treatment is expected to begin with major surgery, perhaps within the next two weeks.

Mickelson, 38, is a double US Masters champion and winner of the 2005 PGA Championship. He and Amy married in 1996 and have three children aged nine, seven, and six.

The situation casts doubt on the world No2's participation in next month's US Open at Bethpage in New York, where in 2002 the big left-hander finished second to Tiger Woods.

Woods said he and his wife Elin "are deeply saddened to hear the news about Amy. Our thoughts and prayers are with her, Phil, the children and the entire Mickelson family".

The spectre of breast cancer has special resonance in golf because Ryder Cup star Darren Clarke's wife, Heather, died of the disease just over two and a half years ago.

Horsey said: "It's been tough. My mum is always at the back of my mind but she has been very strong through it and that's helped me.

"My dad has obviously been there for her, and that's been a big help as well, to know she's got someone at home. I do try hard not to think about it when I'm playing, and what she would want for me is to go and keep on playing.

"Mum is 58 or 59 now, so she's not quite as at risk as, perhaps, Phil's wife or Darren's wife, who suddenly passed away. I've just got to be there for her, support her and, hopefully, she will get through it."

Mrs Horsey follows her son's progress by watching the live scoring on golf internet sites, and his performance today would have been a tonic.

Horsey, who topped last season's Challenge Tour rankings, was brilliant down the back nine, which he tamed in four-under 33, with birdies coming on the last three holes. Among the early starters, his score was matched only by Londoner Anthony Wall, who revealed how, having tamed the greens of Wentworth's West Course, he was off home to mow his lawn.

Wall, who took a break from preparing for the European Tour's flagship tournament by attending Chelsea Flower Show on Monday, said: "To be honest, I'm a donkey at gardening but it gives me a good break from golf."

Oliver Wilson, last year's runner-up after losing a play-off against Spaniard Miguel Angel Jimenez, faces a fight to beat tomorrow's cut after returning a four-over-par 76.

Ernie Els was struggling on two-over coming down the stretch, while new European Ryder Cup captain Colin Montgomerie was level with three to play.

Masters champion Angel Cabrera, of Argentina, opened with a bogey five, as did Lee Westwood, while American John Daly was level par after two.