It wasn't the kind of sequined entrance that blonde Australian pop star Kylie Minogue is famous for. On the night of May 17, the songbird, best known in the States for her chart-topping hit three years ago, "Can't Get You Outta My Head," was looking distinctly unglam. Wearing jeans and a beige sweater as she left her parents' Melbourne home in an Audi limo with an overnight bag stuffed in the trunk, "she looked upset, her hair was unkempt, and she looked like she'd been crying," says one onlooker.

That was understandable. Minogue, who turns 37 on May 28, was heading for Melbourne's St. Frances Xavier Cabrini Hospital just hours after being diagnosed with early-stage breast cancer. The London-based singer, who received the news while taking a break after the European leg of her four-month Showgirl concert tour, canceled her remaining dates in order to begin treatment immediately. "Everyone is shell-shocked," said a close observer. "There was no sense of an underlying drama or illness about to unfold."

At Minogue's side was her boyfriend of the past two years, French actor Olivier Martinez, 39, who played Diane Lane's extramarital lover in 2002's Unfaithful. Just the week before, Martinez, who had flown to Australia for a holiday, was seen frolicking on the beach with Kylie. "During the past week, she seemed in love, happy, relaxed," says one observer.

Minogue, who has long been an active fund-raiser for breast cancer causes, plans to continue her treatment and recovery close by family and friends in Melbourne. Her sister Dannii, 33, also a pop singer, voiced a hopeful note. The cancer news was "very upsetting," she said, "although as [it's] been diagnosed at such an early stage we are all very optimistic that everything will be okay."

That sentiment was echoed by Kylie's fans, who flocked to her Web site to offer best wishes. "Our Min's a tough little cookie," wrote one. "She will pull through."