Brain cyst

Hello,
My 15 year old niece just had a cyst detected in her brain.  She is also being tested for lupus.  The reason her mother was concerned was because my niece began experiencing numbness and pain in her legs last week, to the point that she was barely able to walk.  Over the course of the past year, she's vomited at least once a month, and that seemed to get worse during the past weeks, where she was vomiting once a week.  She also had a severe headache last Monday.  Unfortunately, the neurologist is not being very helpful in the sense that all we're being told is that we don't need to worry about the cyst.  We'd at least like to know where in the brain it's located and how big it is.
So, at this point, we are playing the waiting game, but we'd at least like to know if a cyst in the brain can develop into cancer, or if there is a chance that it will cause complications later in life.
Thanks in advance

[Michael Lim, MD]

In response to your question, do you know what they're calling the cyst (i.e. arachnoid cyst, colloid cyst...etc)?  As for the location, it would be hard for me to comment without looking at the films.  Do you have an except from the MRI report?  Thank you.