Thanks for pointing this out; I did indeed miss out the word 'not'. Sorry!
Cysts can grow, stay the same and get smaller. Mine has grown a tiny amount since I first noticed it a little over a year ago. Your situation definitely sounds like a cyst to me, so it is a bit surprising they didn't say that during your ultrasound. They've reassured you that all is normal, so I'm sure there's nothing to worry about and your Doctor will confirm this when you see her