The "m" word

During another half-sleeping night, I was having semi-conscious nightmares about the "m" word - malignant...  On the day of Zoe's surgery Sean and I glanced at her medical chart and in big letters it said malignant brain tumor (but brain tumor was some fancy term).  This wouldn't have phased us much except for the fact that three separate institutions had the word malignant on her paperwork.  (Fairfax hospital, Children's hospital in DC, and Children's hospital in Philly)  Although Zoe's tumor can't be biopsied, we've been told several times that this type of tumor is likely benign... but why in the world do they keep writing malignant??!!!