How Can You Tell the Difference Between a Cyst and Breast Cancer?

Cancerous breast lumps and breast cysts have some characteristic tactile differences, but they may feel similar enough the only way to really tell one from the other is a diagnostic test like a mammogram or ultrasound.

Breast cysts are fluid-filled round or oval lumps in the breast. There may be one or more, and they can vary in size, number, and symptoms. 

About 25% of all breast masses turn out to be cysts. Most breast cysts are benign (not cancerous) and having them does not increase the risk of developing breast cancer. 

A physical examination alone cannot definitively distinguish between a benign breast cyst and breast cancer. Only a medical examination with tests such as ultrasound can determine whether a lump is a breast cyst or breast cancer.

Breast cysts can occur at any age, but they’re more common for women who are premenopausal. 

Symptoms of breast cysts include: 

• A round lump
• Lump is moveable under the skin
• Lump is often soft in texture but may be felt as a hard mass
  • May be described as grape or water balloon 
• May cause local pain or tenderness that may vary due to hormonal changes during the menstrual cycle 

Fluid buildup inside the breast glands can lead to cysts. Excess estrogen in the body may contribute to their development. 

How Are Breast Cysts Diagnosed?

Breast cysts are diagnosed with a physical examination of the breasts and a patient history. 

• Ultrasound imaging is used to determine what type of cyst is present or if the lump may be breast cancer. 
• Simple cysts have smooth, thin, regularly shaped walls and are completely filled with fluid and are always benign
• Complex cysts have irregular or scalloped borders, thick walls, and some signs of solid areas and/or debris in the fluid
  • Complex cysts may be drained with a fine needle (aspirated) to test the fluid inside can be tested and determine if further testing is needed to rule out breast cancer
• Complicated cysts share most of the features of simple cysts, but also have some debris inside them 

Other imaging tests used to diagnose breast cysts include: 

• Mammogram
• Magnetic resonance imaging (MRI)

Treatment for breast cysts depends on whether the cyst is simple or complicated/complex. 

Treatment for simple cysts is not needed unless the cyst is large, inflamed, infected, or painful. In that case, the cyst is drained with a fine needle. 

For complicated or complex cysts, fine needle aspiration may be needed to drain it and examine the fluid inside. If the doctor feels the cyst has features suggesting it could be breast cancer, a biopsy may be indicated to make sure any solid parts inside the cyst are benign. An excisional biopsy may be performed to remove the cyst for examination.