SAN FRANCISCO — Mimi Lee could handle a fight with breast cancer. But coping with the destruction of frozen embryos that represent her only hope of bearing children may be another matter.

“I want my embryos,” the 46-year-old Lee told a courtroom here on Thursday in a bid to preserve her chance at motherhood. “I want my babies.”

Lee, a Julliard-trained pianist and Harvard educated doctor, took the witness stand for the first time in a divorce trial being closely watched around the nation as a key legal test of spousal rights over frozen embryos when couples split. Stephen Findley, Lee’s ex-husband and a wealthy investment executive, wants the embryos destroyed under agreements the couple signed in 2010 at UC San Francisco’s fertility center, but she is pushing to gain control of them.

Rendered infertile by cancer treatments, Lee was grilled by lawyers for Findley and UCSF about her motivations for her fight with Findley, who sat expressionless as his soon-to-be ex-wife tearfully recounted the collapse of their marriage. Sniffling as she testified, Lee described a relationship that went from Findley proposing marriage with rose petals and champagne on a New York balcony in 2010 to icy conversations about their jointly conceived embryos after they separated more than a year ago.

But Lee insisted she has a simple reason for battling to salvage the embryos, which she described as the most important aspect of the divorce.

“These embryos are for all intents and purposes my last chance to have my own babies,” she testified.

Lee is expected to finish her testimony, and the trial’s evidence stage, on Friday. Superior Court Judge Anne-Christine Massullo has set closing arguments for Aug. 4, and will then issue a written ruling.

The couple has scarcely acknowledged each other during this week’s trial, huddling with their own camps during breaks and making little eye contact. Findley, hobbled on crutches from recent foot surgery, spends much of his time with his father, who has sat in the front row of the gallery each day.

Findley and his lawyer have declined to speak to the media.

On the eve of their September 2010 wedding, Lee was diagnosed with cancer, prompting the couple to rush to UCSF’s fertility center, where five of Lee’s embryos — fertilized by Findley — were cryogenically frozen and preserved for a possible future with children. The couple is now fighting over those embryos in the divorce, which is otherwise finalized, including financial terms.

Lee’s lawyers are urging the judge to find that destroying the embryos would destroy an infertile woman’s ability to “realize the fundamental and constitutionally protected bond of a parent and a child.”

Findley, however, relies on signed documents at UCSF that included provisions for destroying the embryos under various circumstances, including divorce; he considers those agreements a binding contract. Despite the emotional underpinnings of the dispute, the language and force of those agreements are at the heart of the trial.

On Thursday, Lee was repeatedly pressed by lawyers for Findley and UCSF about the fact she signed those agreements, but she insisted she did so in haste and without fully examining the language of the consent forms.

A Bay Area anesthesiologist, Lee testified that she is familiar with such forms in both her professional and personal life, at one point likening signing them to checking off agreements for Apple iOS software upgrades without reading them. She told the judge she doesn’t consider the consent forms a permanent bar to changing her mind.

“We both perused through it,” Lee said of signing the forms with Findley when they sought the fertility treatments.

Findley disputed that contention in his testimony earlier this week, insisting he clearly understood that the embryos would be discarded if the couple divorced. Findley told the judge he cannot envision having the children now, given his contentious relationship with Lee, whom he has accused of trying to extort millions of dollars from him for the embryos.

In Thursday’s testimony, Lee admitted to threatening Findley in angry conversations after they split but said she would never take money in exchange for agreeing to destroy the embryos. “They are priceless to me,” she testified.

UCSF takes the position that its signed directives should be considered “valid and enforceable” by the courts.

Although the trial breaks new ground in California, where the courts have yet to address the question directly, feuding couples in other states have forced the legal system to deal with the modern dilemma of deciding who gets to decide the fate of these stored embryos in the event of a split.

The most high-profile example has been the recent spat between Hollywood star Sofia Vergara and ex-fiance Nick Loeb, who has sued for custody of their stored embryos. And a Chicago appeals court last month ruled in a high-profile case that a woman in a situation similar to Lee’s — she was also left infertile by cancer — could use the embryos despite her ex-boyfriend’s opposition.

Howard Mintz covers legal affairs. Contact him at 408-286-0236 or follow him at Twitter.com/hmintz.