Can a Benign Breast Lump Become Cancerous?

Breast lumps are common, the vast majority are noncancerous and most will not transform into cancer over time. Even so, it is important to promptly discuss any unusual breast mass with a physician who can determine whether it is benign or malignant, usually with the aid of imaging tests and a biopsy.

Some benign breast lumps have the potential to become cancerous if the abnormal cells continue to grow and divide uncontrollably. By viewing a sample of the suspicious tissue under a microscope, a pathologist can determine whether the cells are reproducing faster than normal. If so, the lump will be closely monitored by a physician.

The two main types of noncancerous breast lumps are cysts and fibroadenomas.

What are breast cysts?

A cyst is a fluid-filled sac that may feel like a soft grape under the skin. A breast cyst may be tender, especially immediately before a menstrual period. A physician will typically order an ultrasound scan to determine whether a breast lump is a cyst and, if so, its type.

The two main types of breast cysts are:

Simple breast cysts

Typically smooth, round and filled with clear fluid, simple breast cysts pose no cancer risk, do not need to be removed and may go away on their own. However, if a simple cyst is growing or causing pain, it can be aspirated with a fine needle.

Complex breast cysts

With features such as thickened walls and debris floating in the inner fluid, complex breast cysts are typically monitored with periodic ultrasound scans. In some cases, a cyst may be surgically removed or the fluid within it may be drained.

What are fibroadenomas?

A fibroadenoma is a rubbery breast lump that can be easily moved within the breast tissue. Typically, fibroadenomas develop during a woman’s reproductive years, and most are painless. 

If a physician suspects a fibroadenoma based on a physical examination, they may order follow-up imaging, such as a mammogram and breast ultrasound, to further evaluate the mass. If additional information is needed, the physician may suggest a needle biopsy or surgical removal of the entire lump. A pathologist can then examine the removed tissue under a microscope to check for evidence of cancer. 

Other causes of benign breast lumps

Breast lumps can also result from fibrocystic changes, which are normal variations in breast tissue. Although fibrocystic changes can cause painful, lumpy breasts, they do not increase the risk of breast cancer. Usually, the symptoms worsen immediately before each menstrual period and then improve after the period begins.

A noncancerous breast mass may also be attributed to:

An injury

If the breast is badly bruised, blood may collect under the skin and form a lump (hematoma), which should resolve on its own within a few weeks.

A lipoma

Composed of mature fat cells, a lipoma is a slow-growing fatty mass that can develop within the breast tissue. Typically, the lump is soft, movable and painless to the touch. 

A milk cyst

Also known as a galactocele, a milk cyst may form if milk builds up in a breast duct during lactation or breastfeeding. Galactoceles are typically smooth and round and may feel firm or cystic.

An abscess

Common among breastfeeding women, breast abscesses are pockets of pus that can develop if bacteria enter the breast through a cracked or sore nipple. This type of infection can cause pain, swelling, redness and warmth.

How quickly can a breast lump develop?

The rate at which a breast lump develops can vary widely depending on the underlying cause along with hormonal fluctuations, genetics and other factors. Some breast lumps appear suddenly, while others form gradually over an extended period. A rapidly developing breast lump may be associated with an acute condition, such as a hematoma or abscess.

Is a benign breast lump a cause for concern?

Unlike a cancerous breast tumor, which can potentially invade nearby tissues and spread to distant organs, a benign breast mass is not life-threatening, cannot spread or metastasize and may not require treatment. After diagnosing a noncancerous breast lump, a physician may suggest a “wait-and-watch” approach to monitor the mass for changes. If the mass grows large enough to cause discomfort or press on a vital structure, such as a nerve or blood vessel, its surgical removal may be considered.

Can the prognosis change over time?

In some cases, it may be unclear whether a breast lump is benign or malignant, leading to an uncertain diagnosis that requires ongoing follow-up. Additionally, it is possible that a biopsy could identify precancerous cells or miss an area of tissue in which cancerous cells are more prevalent. In any of these scenarios, a lump that was initially believed to be benign could later be identified as malignant after it further grows and develops.

How fast do breast tumors grow?

Most cancerous breast lumps grow for several years before they become large enough to be felt or seen in a mammogram. Then, they seemingly appear spontaneously and continue to grow steadily in size.

Benefit from world-class care at Moffitt Cancer Center

If you would like to have a breast lump evaluated by a specialist in the Don & Erika Wallace Comprehensive Breast Program at Moffitt, you can request an appointment by calling 1-888-663-3488 or submitting a new patient registration form online. We do not require referrals.