She had it removed? Why? Breast cysts should evaporate on their own. Fibrocysts are different, but even a doctor can tell that without any further testing.
Typically when you find a breast lump, a mammogram and ultrasound are scheduled. The mammogram can confirm immediately whether it's a tumor (whether it's benign or malignant is another story, and needs to be tested via biopsy.) A tumor shows up as a grey-white matter, whereas a cyst won't even show up on a mammogram. Then, an ultrasound usually follows to confirm that it's a cyst - they show up as black because they're fluid-filled, usually.
I've had those, and have gone through this process myself. I'm extra-viligant because of a very strong family history of breast cancer.
I know you're worried about your aunt. I sympathize with you, totally. Wait until she has either a mammogram or ultrasound first so you all know where to go from here.