O'Connor, who found herself back in the spotlight early last year when she admitted to gambling away as much as $13 million, underwent the procedure at the Sharp Memorial Hospital Outpatient Pavilion.
O'Connor, the mayor from 1986-1992, will remain hospitalized for observation for another day, according to Sharp Healthcare, which characterized the procedure as successful.
In a statement released through the hospital, the 68-year-old O'Connor encouraged San Diego women to consult their physicians and learn more about breast cancer screening and early detection.
In February 2014, O'Connor agreed in federal court to pay back $2 million to a charitable organization founded by her late husband and seek treatment for a gambling addiction. Her lawyer, Eugene Iredale, said O'Connor played video poker at casinos.
The attorney said OConnor had a brain tumor removed in 2011.
She's the second major local political figure to be treated recently for breast cancer. Councilwoman Marti Emerald was diagnosed with the disease last year.
Emerald, who has said her prognosis is good, announced last week that she would not seek reelection so she could move on to the next stage of her life.
