Marjane Green might never have found the tumor in her left breast if she hadn't felt a pain in her right breast.

The Houston-area resident wasn't too concerned since she'd had a mammogram just two months earlier. And, she had been dealing with recurring cysts in her breasts for more than 30 years as a result of hormone therapy following a hysterectomy. But this pain was different than anything she'd felt before.

Marjane's...