A simple cyst or a complex one
This distinction matters a great deal, and it is made by breast ultrasound alone. Examination by hand cannot separate a simple cyst from a complex one.
Filled entirely with fluid and thin-walled. Entirely benign: it does not turn into cancer and does not raise the risk of cancer. It usually needs no treatment; if it is very large and painful it can be drained with a syringe.
A cyst containing a solid area or with a thickened wall. It calls for close follow-up and, in some cases, a biopsy.
What fibrocystic breast tissue is
If you have many cysts, this is called fibrocystic breast tissue. It is not a disease but the make-up of the breast, and it does not raise the risk of cancer.
It does, however, make examination and the reading of a mammogram harder, which is why regular ultrasound follow-up matters. We set the schedule together.