"What bears emphasizing is that: a) this is incredibly rare, and teenagers need not worry about this happening to them; and b) physicians need to be aware that, while rare, this can happen, so that new lumps should be taken seriously," said Dr. George Sledge, professor of Medicine and Pathology at the Indiana University School of Medicine in Indianapolis and editor-in-chief of the journal Clinical Breast Cancer.
Lichtenfeld agreed. "Hannah's case, which thankfully appears to be having an excellent outcome, is extremely unusual and should not be cause for undue alarm," he said. "As with any health issue, parents who are concerned about any seemingly unusual physical change should talk to their family's health care professional."
Likewise, Hannah told KCAL that she hopes her experience will help other children like her keep open lines of communication with their parents when it comes to health issues.
"I want to set an example for all the kids in the world, that if there's something wrong with your body, you tell your parents," she said.
Michelle Schlief and the ABC News Medical Unit contributed to this report.