What causes breast cysts?
We often attribute slight irregularities or areas of tenderness in breast tissue to a process called fibrocystic disease. Fibrocystic disease is a process that occurs in the breasts of women. It has nothing to do with cysts elsewhere in the body or fibroid tumors of the uterus. Often, fibrocystic disease can cause a cyst (a cyst is a fluid filled pocket) in the breast. The diagnosis of this is made either by ultrasound or by removing the fluid with a needle and syringe.

If we can feel the cyst we usually remove the fluid with a needle to confirm the fact that the lump that we feel is indeed a cyst. We prefer not to leave a patient with a lump in the breast unless we are 100% certain of the diagnosis. We do not usually do anything more to evaluate this once we have confirmed that it is a cyst. 

If we can not actually feel the cyst, but only see it on mammogram or ultrasound, we may just observe it if the radiologist feels that it is a simple cyst.

• Removal of a cyst is  indicated if: 
• There is a lump remaining even after the fluid is removed.
• The cyst keeps coming back.
• The cyst contains bloody fluid which tests suspicious for cancer.

The fluid that is removed is not usually sent for any additional tests unless it is bloody, since researchers have found that there is essentially no chance of finding cancer in the cyst fluid if there is no lump left and the fluid is not bloody in color.