Is this really a benign cyst or cancer?

I am a 43 year old woman with a strong history of breast cancer in my family ( mother and two aunts).  The past three years a cyst has been visible on my mammagram increasing in size each year.  My left breast is increasing in size too.  A ultrasound was performed the last year assuring me this was a benign situation.  No biopsy was done.  I am going for a mammagram in two weeks, should I insist on a biospy or futher testing if the cyst have grown again.  I feel like something is wrong but I don't know what to do?

[CCF-RN,MSN-JS]

Dear jdo, There are findings on the exams that may lead the radiologist to interpret the results as more or less suspicious.  A cyst is fluid-filled, usually smooth like a marble and distinct.  An ultrasound is a test that helpful in determining if something is fluid-filled or not.  Having said this if you are further concerned about the interpretation of results with this next mammogram, an option would be to seek a second opinion with a breast specialist.  A biopsy would be the next step in terms of being more sure about the findings.