From 2000 to 2015, there was a more than 4% increase each year of stage 4 breast cancer cases in women under 40. That's according to a study published in the journal Radiology. Researchers who worked on the study say that's significant. Senior medical correspondent Dr. Tara Narula shares the story of a 30-year-old woman who has stage 4 breast cancer and looks at what may be behind this concerning trend.
