If you have a copy of your us report, you should be able to tell the difference.
Try not to worry as most cysts
do turn out to be benign (even large ones). But, if you cyst
is over 5cm and complex, it is more worrisome for malignancy. Even if this were the case, most of these also turn out to be benign. But, you will be facing surgery to remove it. The only way to determine the type of cyst is to remove and biopsy it.