Breast cancer does not have one simple cause. Risk develops from a combination of factors, some of which can change and some of which cannot.

Age, inherited genetic changes, family history, reproductive history, previous medical treatment, alcohol use, physical activity and other factors can all play a role. Having a risk factor does not mean a person will develop breast cancer, and someone can develop breast cancer without a major known risk factor.

Why does age matter?

Breast cancer risk generally increases with age. The CDC notes that most breast cancers are found in women age 50 or older.

That does not make younger age a guarantee of safety. Younger people can also develop breast cancer, which is why an unusual breast change should not be dismissed simply because someone is young.

Age changes probability. It does not provide a yes-or-no answer for an individual person.

What can increase risk?

Some risk factors cannot be changed. These include age, certain inherited genetic changes, family history and some previous medical exposures.

Family history becomes particularly important when several close relatives have had breast or ovarian cancer or when an inherited change such as BRCA1 or BRCA2 is present. That does not mean a person with family history will develop cancer. It may mean their risk assessment deserves more attention.

Other factors can sometimes be changed. Physical inactivity and alcohol use are associated with increased breast cancer risk, while some reproductive and hormone-related factors also influence risk.

Risk is individual. It is usually misleading to point to one behavior and say it caused a person's cancer.

What warning signs should be checked?

Possible breast cancer symptoms can include:

  • a new lump in the breast or underarm
  • thickening or swelling
  • changes in breast skin such as dimpling or irritation
  • redness or flaky skin around the nipple
  • a nipple turning inward
  • unusual nipple discharge, including blood
  • a change in breast size or shape
  • pain in an area of the breast

These signs can have many causes that are not cancer. The important point is not to diagnose yourself from a symptom list.

A new, unusual, or persistent change deserves appropriate medical assessment. Some people with breast cancer have no symptoms, which is one reason screening recommendations matter.

What can reduce risk?

There is no guaranteed way to prevent every case of breast cancer.

Risk reduction can include staying physically active, limiting alcohol where appropriate, understanding family history, and discussing individual risk with a healthcare professional. Depending on someone's circumstances, a clinician may discuss screening schedules or additional risk-reduction options.

The goal is not to become frightened by every normal variation in the body.

It is to know what is usual for you and to have persistent or concerning changes checked.

What should a partner know?

A partner may notice a change before the person does, or may become worried after hearing a frightening story.

The most useful response is usually neither panic nor reassurance without evidence.

A simple conversation can be enough:

“I noticed something has changed. Would you like help arranging a medical check?”

That shows concern without pretending to know what the change means.

Questions people often ask

Does having a risk factor mean someone will get breast cancer? No. Risk factors change probability; they do not determine an individual's outcome.

Is every breast lump cancer? No. Many breast lumps and changes have causes other than cancer.

When should someone seek medical advice? A new, unusual, or persistent breast change should be assessed by an appropriate healthcare professional rather than diagnosed from an online article.

This article is general educational information and is not a substitute for individualized medical care.