Where Does Breast Cancer Spread?

When breast cancer spreads beyond the breast to other organs in the body, it is called metastatic breast cancer. Despite where the cancer may spread, it is still considered breast cancer, as the cancer is named for where it originated.¹ Approximately 5-10% of women with breast cancer have MBC when they are diagnosed,^2,3 and an estimated 20-30% of people who are initially diagnosed with early stage breast cancer have their disease recur and/or develop into metastatic breast cancer.⁴

Breast cancer metastasizes, or spreads, by cancerous cells breaking off from the original tumor and spreading through the body via the bloodstream or lymph system. While metastatic breast cancer can spread to various parts of the body, it most commonly spreads to the following organs¹:

• The bones
• The liver
• The lungs
• The brain

Breast cancer may also spread locally, which is also known as locally advanced breast cancer. In locally advanced breast cancer, the cancer can spread to the nearby lymph nodes (the axillary lymph nodes under the arm, or the supraclavicular and infraclavicular lymph nodes above and below the collarbone, respectively), the skin of the breast, or it may spread to the chest wall, invading the muscle and connecting tissues underneath the breast.¹

Figure. Common locations of breast cancer metastasis

Bone metastases

When breast cancer metastasizes to the bones, it may be called metastatic breast cancer with bone metastases, or “bone mets.” Breast cancer can potentially metastasize to any bone in the body, although it commonly spreads to the ribs, spine, pelvis, and/or the bones in the arms or legs.⁵

When breast cancer metastasizes to the bone, it can cause symptoms such as^5,6:

• Pain in the affected bone
• Bone fractures or breaks
• Swelling
• Fatigue
• Nausea
• Loss of appetite
• Dehydration

While pain in the bones from bone mets may be difficult to distinguish from arthritis pain, any new sudden pain should be evaluated by a healthcare professional. Prompt treatment of bone metastases can help prevent fractures.⁵

Bones are the most common site for metastasis from breast cancer, and one study found that bones were the first site of metastasis for 46% of study patients. In the study, 71% of patients with metastatic breast cancer developed bone metastases. The researchers also found that overall survival was longer (median of 71 months vs 48 months) for those patients with bone metastases at first relapse versus patients with visceral metastases (spread to other organs such as the liver or lungs) at first relapse.⁷

Liver metastases

Breast cancer metastasis to the liver, or “liver mets,” can cause symptoms such as^6,8:

• Jaundice, a yellowing of the whites of the eyes and the skin
• Itchy skin
• Pain or swelling in the abdomen or under the rib cage on the right side
• Weight loss
• Loss of appetite

However, when breast cancer spreads to the liver, it may not cause any symptoms at first. The first signs may be picked up by blood tests, which measure the levels of certain enzymes and proteins that fluctuate depending on how the liver is functioning.⁸

Lung metastases

When breast cancer spreads to the lungs, it can cause symptoms such as^6,9:

• Difficulty breathing or shortness of breath
• A constant dry cough
• Wheezing
• Pain in the lungs

However, breast cancer in the lungs may not cause symptoms when it first spreads there. Lung metastases, or “lung mets,” may be first found on a scan, such as a chest x-ray or computed tomography (CT) scan.⁹

Brain metastases

Breast cancer that spreads to the brain, also called “brain mets,” can cause symptoms such as^6,10:

• Headache
• Confusion or memory problems
• Seizures
• Dizziness or loss of balance
• Vision changes
• Changes to personality or mood
• Slurred speech

Approximately 10-15% of women with metastatic breast cancer develop brain mets.¹⁰