If the discomfort began soon after a new workout or physical activity, muscle strain is one possibility.

This is also why the location of discomfort alone does not always tell you which structure is responsible.

A healthcare professional can examine the area and determine whether the pain appears to originate from the breast itself or the tissues underneath it.

4. Cysts Can Cause Localized Discomfort

Breast cysts are fluid-filled sacs that can develop within breast tissue.

They are relatively common, particularly during certain stages of life, and many are benign.

Some cysts cause no symptoms.

Others may feel like a lump and can become tender or painful, especially around hormonal changes.

A cyst may feel smooth or somewhat movable under the skin, although texture alone cannot reliably identify what a lump is.

That is important.

People sometimes try to diagnose a breast lump by touching it and deciding whether it feels “soft,” “hard,” or “round.”

Those characteristics can provide information, but they are not enough to establish a diagnosis.

If you notice a new lump, a persistent area of thickening, or localized discomfort that does not go away, professional assessment is appropriate.

A clinician may recommend imaging such as ultrasound or mammography depending on age, symptoms, and medical history.

5. Fibrocystic Breast Changes Can Cause Tenderness

Some people have breasts that naturally contain areas of lumpy or nodular tissue.

These changes have sometimes been described as fibrocystic breast changes.

The tissue can feel uneven, dense, or rope-like, and tenderness may fluctuate with hormonal changes.

Again, not every lumpiness is abnormal.

Breast tissue varies considerably from person to person.

However, there is an important distinction between knowing that your breasts normally feel somewhat lumpy and discovering a new or distinctly different change.

Knowing your own normal breast appearance and texture can help you recognize something that deserves examination.

If you notice a new lump or a persistent change, do not assume it is simply “fibrocystic tissue.”

A clinician can determine whether further evaluation is necessary.

6. Infection Can Cause Pain, Redness, and Warmth

Breast infections can also cause discomfort.

One example is mastitis, which is more commonly associated with breastfeeding but can occur in other circumstances as well.

Symptoms may include:

• Localized pain

• Redness

• Swelling

• Warmth

• Tenderness

• Fever or chills

A bacterial infection may require medical treatment.

If a breast becomes suddenly painful, red, swollen, and warm—particularly when accompanied by fever—it is important to seek medical advice.

People who are breastfeeding may develop mastitis when milk flow is disrupted or bacteria enter through a damaged nipple.

Breast infections should not be confused with ordinary hormonal tenderness.

The symptoms and physical findings tend to be different.

7. Skin Irritation Can Create Burning or Tenderness

Sometimes the source of discomfort is the skin rather than deeper breast tissue.

New detergents, lotions, perfumes, soaps, deodorants, fabrics, adhesives, or other products can irritate sensitive skin.

You may notice:

Itching

Redness

Dryness

Burning

Peeling

A rash

Friction and sweating can make irritation worse.

This can happen under the breast as well, especially in warm or humid environments.