In 2009, Hallie Leighton received “normal” results from a mammogram. In 2010 she was diagnosed with cancer and also told it was there in 2009, at this point it was Stage 4. She passed away in 2013. Every women in her family had been diagnosed with breast cancer, prompting her to start getting mammograms at age 35. However, she had dense breast tissue making her cancer undetectable until it became fatal.