Pain Under Left Breast – Causes of Pain Below Breast on Left Side

Pain in the torso can at times be difficult to identify. The chest, abdominal and pelvic cavities contain many organs, all of which can be the source of pain when damaged or diseased. Similarly the pain can arise from the different structures that make up the surface (chest or abdominal wall), such as the skin, muscles, fat, connective tissue and bones where present.

Therefore identifying the cause of the pain can be difficult without considering the location and accompanying symptoms. Most of us refer location in reference to some other point in the body. Pain under the left breast is one such example. However, this location can vary due to the differences in breast size and shape between males and females. Furthermore there may also be variances in the female breast for several possible reasons.

Location of Pain Under the Breast

As mentioned, there may be some degree of variance in the location of pain under/below the breast. With regards to the left breast, this usually refers to the lower left region of the chest cavity and the upper left region of the abdominal cavity. Organs in these regions include:

  • Chest:
    – Lung and pleura
    – Heart, great vessels and pericardium
    – Esophagus
  • Abdomen:
    – Stomach
    – Spleen
    – Kidney and ureter
    – Adrenal gland
    – Pancreas
    – Liver

In most cases, only part of the abovementioned organs lie within the region under the left breast. The diaphragm is a flat sheet of muscle that separates the chest and abdominal cavities. Skin, muscles, bones and other tissues that comprise the walls of these cavities may also be a source of the pain. Furthemore, pain may radiate or refer from other parts of the body. Therefore pain under the left breast may not be due to any problem in this region of the torso.

Read more on pain under the left rib cage.

Causes of Pain Under the Left Breast

There are a number of different causes of pain under the left breast. Sometimes diseases within the breast may cause breast pain that can radiate or refer to the region under the affected breast. Therefore the causes of breast pain should also be considered. Some of the other causes of pain under the left breast have been discussed below. These are among the more common causes but various other conditions may also be responsible.

Read more on causes of breast pain.

Chest and Abdominal Wall

Injury to the chest and abdominal wall are common causes of superficial pain in these areas. It may arise from blunt force injury or penetrating injuries. Muscle strain is another common cause of chest and abdominal wall pain. Infections of the chest and abdominal wall are more likely to involve the skin. A pinched nerve and other nerve conditions like shingles may also be responsible for surface pain under the left breast area.

Heart and Great Vessels

The heart lies in the middle of the chest and extends to the left. Around it lies the pericardium and large vessels run to and from the heart. Conditions affect any of these structures may cause pain under the left breast. A heart attack (myocardial infarction) is one of the more serious conditions that can cause pain in this region. There may be preceding attacks of pain due to limited blood flow to the heart (angina pectoris) that can also be responsible.

Read more on common heart problems.

A number of other heart problems may also be responsible for pain in this region. Aneurysms, tears and inflammation of the great vessels can also cause pain. The lining around the heart may also become inflamed. This is known as pericarditis and is most often due to infections. Tumors of the heart are not common but can occur. Some may be benign (non-cancerous) while others may be malignant (cancerous).

Lungs and Pleura

The left lung lies behind the left breast running from above it to the bottom end of the chest cavity. The pleura isĀ  a membrane that surrounds the lungs. Conditions affecting the lungs, particularly the base of the left lung and the surrounding pleura may therefore cause pain under the left breast. This includes conditions like pneumonia, hypersensitivity pneumonitis, pneumoconiosis, pleuritis, lung cancer and cancer of the pleura like mesothelioma.


Most of the stomach lies in the upper left abdominal region (LUQ ~ left upper quadrant) which is largely under the left rib cage. Gastritis and peptic ulcer disease are two of the common conditions that can cause persistent or repeated pain the stomach. Less common conditions like stomach cancer may also be responsible. A Mallory-Weis tear and hiatal hernia are two upper stomach conditions that are more likely to cause pain closer to the breast.


The esophagus runs down the chest cavity to pass through an opening in the diaphragm and continues with the stomach. Conditions affect the lower part of the esophagus may be perceived as pain under the left breast, more towards the midline. Esophagitis is a common condition that often arises due to acid reflux. This may also lead to ulcers in the esophagus. Cancer of the esophagus is a less common but possible cause of pain.


The pancreas lies in the upper middle abdominal region, running from right to left. Conditions affecting the body and tail of the pancreas may be responsible for pain under the left breast. Pancreatitis is one of the more common pancreatic conditions to cause pain in this region. Pancreatic pseudocysts and pancreatic cancer are some of the other possible conditions to cause pain under the left breast.


Most of the liver lies in the right upper quadrant of the abdomen. A smaller portion extends across the midline to the left upper quadrant of the abdomen. Conditions like hepatitis are more likely to cause liver-related pain in the region under the left breast. Liver cancer is a less common but serious condition that may also present with pain under the left breast. A common condition known as fatty liver disease may cause liver pain in some people.

Other Causes

  • Kidney: Pain is felt more towards the side and back of the left flank. Conditions may include pyelnephritis, kidney stones and renal carcinoma (kidney cancer). Adrenal problems may also be responsible.
  • Spleen: Pain in the left flank may be due to the spleen. Common spleen conditions like an enlarged spleen (splenomegaly) rarely causes pain. Most likely causes are spleen inflammation (splenitis) or ruptured spleen.
  • Peritoneum: The peritoneum lines most of the abdominal organs and the inner wall of the abdomen. When it becomes inflamed (peritonitis) it can lead to acute abdominal pain.
  • Bowels: Although the bowels lie lower, conditions of the left half of the transverse colon and splenic flexure may cause pain under the left breast. Conditions like inflammatory bowel disease (IBD), diverticulitis, trapped gas and impacted feces may be responsible for pain in these aeas of the colon.

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