Fibroadenomas: 

These are solid, noncancerous lumps that often occur in women before menopause.  A fibroadenoma is a smooth, firm, well defined lump.  It moves easily under your skin when touched and is usually painless.  They can get bigger during pregnancy and breast-feeding.

• Symptoms:  These solid breast masses are usually firm or rubbery, are round with distinct borders, move around easily and are painless.  They usually grow to about 1 to 2 centimeters in size, but can become even larger.  A fibroadenoma that is larger than 5 cm is called a giant fibroadenoma.
  
  
• Causes:  The cause of fibroadenomas is mostly unknown, but it is probably related to reproductive hormones.  This is supported by the occurrence most often during your reproductive years and shrinking or disappearance after menopause.
  
  
• Risk factors:  Most fibroadenomas are simple fibroadenomas and do not increase your risk of breast cancer.
  
  
• Tests and diagnosis:  After a lump has been discovered, your doctor will do a clinical breast exam.  A mammography and/or breast ultrasound can be ordered next.   If you are younger than 30, your doctor may opt for an ultrasound rather than a mammogram.  This is because younger women have very dense breast tissue which makes mammograms more difficult to interpret.  An ultrasound is a very good test for determining the difference between a solid and a cystic mass.  To be certain that a solid mass is a fibroadenoma and not breast cancer, your doctor will probably recommend a biopsy. 
  
  
• Surgery:  If your doctor is reasonably certain that your breast lump is a fibroadenoma and not breast cancer-based on the results of the clinical breast exam, imaging test or biopsy-surgery may be unnecessary.  You doctor might recommend surgery to remove the fibroadenoma if one of those tests is abnormal.  You may also consider surgical removal if leaving a fibroadenoma in place makes you anxious.