Tina Knowles reveals breast cancer diagnosis, says missed mammogram may have delayed detection

Tina Knowles, mother of Beyoncé and Solange, is opening up about her recent battle with breast cancer in a deeply personal interview with "CBS Mornings" co-host Gayle King.

The 71-year-old said she was diagnosed with Stage 1 breast cancer in her left breast after doctors discovered two tumors during a delayed mammogram appointment.

"I've always tried to take care of myself. I just … was in disbelief," she told King.