Bambam45, I know it's easy to say but don't worry about breast cysts, they are nothing whatsoever to do with cancer, they are sacs of liquid that change in size sometimes, that's all. This is a post I wrote recently:
"Regarding breast cysts, they are extremely common and women can have them for years without knowing about them and many didn't show up well on old fashioned mammogram equipment - some have only become easy to detect more recently with more modern ultrasound equipment. I have had them in the past and always have an ultrasound straight after a mammogram and the specialist said that in his entire career, he has never seen a breast cyst turn into a malignancy. He said there are benign breast lumps that can turn malignant but they are not breast cysts (they have another name which I can't remember) and as CLKD says, if lumps are at all suspicious, they should always be removed immediately."
Apparently up to 1 in 3 women between 30 and 50 have breast cysts.
I hope this reaches you before your appointment - while you are there, why not speak to someone about your concerns so that they can put your mind at rest.
Good luck!