My daughter-in-law has been having trouble with migraines and after many tests and numerous MRIs they decided the lone spot they found in her brain was a cyst. She was told much the same as you.
Did he call it an epidermoid cyst or an arachnoid cyst? If you get the report and see what he called it, you can google it and read up on it. Yes, these are congenital cysts.