What causes breast lumps?

Throughout life, your body changes — and that includes your breasts. When you notice a difference in how your breasts feel, it’s not necessarily cause for alarm. Most breast lumps are harmless. And there are so many things that could be behind them. Here’s what to know.

What are breast lumps?

“Breast lumps are masses that develop within your breast,” says Robin Skrine, MD, breast surgeon at Geisinger. “You may notice an actual lump or just swelling.”

Breast lumps may feel different than your actual breasts. These painless growths can feel:

• Soft
• Hard
• Moveable
• Smooth
• Bumpy

“They can come in many shapes and sizes,” says Dr. Skrine.

Causes of breast lumps

Most breast lumps, also called masses, are non-cancerous — and they have many different causes, Dr. Skrine says, including:

Fibrocystic changes

Your hormone levels fluctuate, particularly during your menstrual cycle, which can lead to areas of temporarily lumpy breast tissue. These lumpy areas may feel tender or sore.

Cysts

“Cysts are fluid-filled sacs that form within breast tissue,” says Dr. Skrine. They’re more common in pre-menopausal women.

Fibroadenomas

These benign lumps are common in women in their 20s and 30s. They can change size over time. And they may disappear completely. Your provider may choose to monitor them for changes.

Mastitis

Mastitis is a breast infection most common in breastfeeding women. Breast infection may lead to the formation of an abscess, a benign mass in your breast.

Lipomas

These non-cancerous fatty tumors form inside breast tissue. 

Breast injury

An injury to your breast can also lead to a mass that you can feel.

Breast cancer

Breast cancer can cause masses too, of course. However, it’s a less common cause. “Having a breast lump doesn’t mean you have cancer,” says Dr. Skrine. “Just be sure to speak to your healthcare provider if you notice changes in one or both of your breasts that last more than a month.”

Who’s at risk for breast lumps?

Anyone can have a breast mass. But you’re more at risk if you:

• Have dense breasts
• Have a history of breast lumps
• Use hormone replacement therapy (HRT)
• Are between ages 18 and 35
• Are pregnant or in menopause

When to see a healthcare provider

Many breast lumps go away on their own without treatment. However, contact your healthcare provider if you have a lump that:

• Appears in your breast or armpit
• Doesn’t go away after a few weeks
• Changes shape, size or color
• Feels hard

Other reasons to seek medical advice include:

• Nipple inversion or discharge
• Any changes in how your breast looks or feels

Your provider can do an exam or order breast imaging to take a closer look. They’ll provide information and treatment for your breast condition, or refer you to a specialist.

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