Pain In or Under the Left Breast

Pain under or in the left breast could have many possible causes, such as injury, infection, hormones, and lung problems. Sometimes left breast pain can be related to your heart, so it's important to first rule this out before considering other causes.

This article will walk you through the causes of left breast pain, the other symptoms to watch for, and when to see your healthcare provider.

Heart-Related Causes of Pain in the Left Breast

Some causes of left breast pain are related to the breast itself. Others are not. Because left breast pain can be a symptom of a heart attack, however, it is important to rule out this cause first.

Heart Attack Symptoms

The symptoms of heart attack in females may include:

• Mild pain
• Burning
• An uncomfortable feeling in the breast

These are often different than symptoms of a heart attack in males. Unfortunately, the often vague and subtle symptoms lead women to overlook the signs. Too often, that's a fatal mistake.

Everyone should be familiar with the symptoms of a heart attack. They may include:

• Chest pain or pressure (not present in up to a third of people having a heart attack)
• Pain in your neck, jaw, or left arm
• Shortness of breath (especially common in women)
• Sweating
• Nausea
• Lightheadedness or passing out
• A feeling that something isn't right or a sense of impending doom

If you're not sure where your pain is coming from, get immediate medical attention. Call 911 if you think you may have symptoms of a heart attack.

The Origin of Left Breast Pain

Left-sided breast pain can originate in the breast itself or in other nearby structures. It can be hard to pinpoint the source.

The location of pain isn't always the same location as the problem. Some nerves are very specific. For example, if you feel a sensation on your fingertip, it's likely caused by something at that site.

Other nerves aren't as specific. They alert you to the general area of a problem, not the precise location.

It's common not to know whether your pain is in your breast or in something close to it.

Breast-Related Causes

Several breast conditions may cause pain in or under the left breast. They include:

• Injuries such as muscle strain
• Breast surgery
• Milk duct conditions and infections
• Hormonal causes
• Lumps

Injuries

Your breasts are covered with sensitive, elastic skin that protects:

• Nerves
• Blood vessels
• Connective tissues
• Ducts and lobes for producing breast milk

If you've had a breast injury, bruising and aches may last until the injury heals.

Sometimes an injury to the breast causes scar tissue. Scar tissue can cause pain and fat necrosis, a breakdown of fatty tissue. It may appear as a hard lump. These lumps are hard to distinguish from breast cancer, even on a mammogram.

Breast Surgery 

After any type of breast surgery—augmentation, reduction, or reconstruction—your breasts will hurt as the incisions heal and scar tissue develops.

As with scar tissue from an injury, pain can come and go long after your surgery. Depending on the type of surgery, you may experience:

• Burning pains in your nipples
• Sharp, shooting pains in your breast
• A tightness or cramping sensation in your breasts, shoulders, neck, and back
• Nerve pain (burning, pricking, or shock-like sensations) in the breast, chest, arm, or armpit

Milk Duct Conditions and Infections

Several benign but painful conditions can develop inside your breast milk ducts.

• An abscess under your nipple or areola can cause pain, redness, and heat.
• Milk ducts can become clogged, causing a firm, tender lump.
• Mastitis is an infection in a clogged duct. It makes the breast swollen, tender, warm, and red.
• Ductal ectasia is another possible infection. It causes tenderness, irritation, redness, and possibly a thick, sticky discharge from the nipple.
• Breast cysts and fibroadenomas are growths that may crowd breast structures, creating aches and pains.

Hormonal Causes

Hormone changes may cause breast tenderness. That's especially true during the fluctuations of your menstrual cycle. 

Other causes include taking hormones for:

• Oral contraception (birth control pills)
• Infertility treatments
• Hormone replacement therapy

You may feel pain in one or both breasts. It may be worse on one side. You might also feel it in your armpit.

Some thyroid diseases can lead to benign (noncancerous) breast changes that cause pain. These include:

• Hypothyroidism (low thyroid hormones)
• Graves' disease (an autoimmune disorder involving excess thyroid hormone)

The nature of the pain depends on the specific breast changes.

Lumps

Breast lumps can show up at certain stages of your menstrual cycle. If you find lumps at other times, see your healthcare provider right away. It's even a good idea to get lumps that are related to your cycle checked out.

Your provider can take the steps necessary to see whether a lump is benign or malignant (cancerous). They'll likely use imaging tests and possibly a biopsy.

Left-Sided Breast Cancer

Breast cancer is usually—but not always—painless in the early stages. A notable exception is inflammatory breast cancer.

That's an aggressive breast cancer that usually begins with:

• Pain
• Redness
• Swelling in the breast

This cancer often resembles an infection. Most of the time, you can't feel a lump. The only early symptom may be the pain in one breast.

Breast cancer in female breast tissue occurs slightly more often on the left side than the right. (It occurs equally on both sides in male breast tissue.)

Breast pain is likely due to something other than cancer.

Non-Breast Related Causes

It can sometimes be hard to tell where pain is centered. You may feel it in your left breast while it actually comes from beneath it.

Some non-breast conditions you may feel in your breast include:

• Chest injury
• Costochondritis or Tietze syndrome
• Pericarditis
• Esophageal causes
• Lung-related causes
• Fibromyalgia
  

Chest Wall Pain

Below your breast are chest wall muscles. They may spasm when you're anxious or stressed. That can cause pain that lasts for a few seconds or several days. You may also experience chest wall pain if you strained a muscle in your chest or you have a bruise or rib fracture.

Chest wall pain from inflammation of the cartilage between the breastbone and ribs is called costochondritis. It is similar to another condition called Tietze syndrome, which can also cause local swelling.

Chest wall pain can also be caused by precordial catch, a benign condition associated with brief, sharp pain on the left side of the chest.

Chest wall pain can appear on either side, though it's less common on the right. It can range from mild to severe. It's usually painful to the touch. The pain may radiate to your back or stomach and can feel sharp or stabbing.

It may get worse when you take a deep breath. Pains may even shoot down your arms.

Esophageal Causes

Your esophagus is the tube that connects your mouth and stomach. It runs below your left breast.

Sometimes gastroesophageal reflux disease (GERD) can feel like left breast pain. A related condition called hiatal hernia may cause similar symptoms.

Pain from the esophagus may be a burning pain, like heartburn. You may have other symptoms like an acidic taste in your mouth.

Other digestive system conditions, such as liver disease, may at times cause pain that feels like it's in your breast.

Fibromyalgia

Fibromyalgia is a chronic pain condition. It can cause pain anywhere in your body. Chest pain, including costochondritis, is fairly common.

Fibromyalgia pain comes from a disordered nervous system. It affects not only nerves, but muscles, joints, and connective tissues. The pain it creates can be generalized and diffuse or sharply focused.

The nature of the pain can be dull and achy, sharp, stabbing, burning, or tingling. Fibromyalgia pain is notably not tied to inflammation, redness, or warmth.

Very often, fibromyalgia pain is made worse with gentle pressure. This is called tactile allodynia.

Lung-Related Causes

Your lungs sit behind your breasts. A few lung-related conditions can cause pain that's mistaken for breast pain. They include:

• Pneumonia: A lung infection that causes inflammation in the air sacs
• Pleurisy: An inflammation of the membrane that covers your lungs
• Pulmonary emboli: Blood clots that travel to your lungs
  

Other symptoms of a pulmonary embolism include sudden shortness of breath and coughing. Pulmonary emboli are medical emergencies that require immediate treatment.

Skin-Related Causes: Shingles

Sometimes pain feels like it's either in the skin or on the outer surface of the breast. This may be shingles.

That's a condition caused by reactivation of the virus that causes chickenpox (the varicella-zoster virus). It can come on years or decades after you have chickenpox.

The initial tenderness is generally followed by a painful rash. Because the rash is the more recognizable symptom, shingles can be hard to recognize early on.

When to Get Medical Help

Left-sided breast pain has many causes. Some are more serious than others. The only way to know for sure what's causing your pain is to get medical attention. 

Pain is your body's way of alerting you to a problem. Don't ignore it or assume it's harmless.

If your healthcare provider doesn't find an explanation for your pain, keep pushing for one. If pain persists, consider getting a second opinion.

It's not unheard of to have more than one cause of left breast pain. For example, you may have a breast cyst along with costochondritis.

Summary

The first thing to do when you have left breast pain is get checked for a heart attack.

Left breast pain can come from injuries or conditions that affect the breast tissue and milk ducts. Breast cancer isn't usually painful early on. An exception is inflammatory breast cancer, which also causes redness and swelling.

Pain from other areas felt in the left breast can come from nearby structures like chest muscles, the lungs, or the esophagus. Nerve pain in the area can be from fibromyalgia or shingles.

See your healthcare provider about left breast pain so you can have it diagnosed and treated.

A Word From Verywell

Left breast pain may lead your mind straight to breast cancer. Rest assured most breast pain isn't cancer-related.

Even so, be sure to get pain or suspicious lumps checked out right away. An early diagnosis and treatment are best when the cause is serious.

Even if your left breast pain isn't a symptom of a serious condition, you'll feel better once it's gone. See your doctor, get a diagnosis, and follow treatment recommendations.