Breast cancer most commonly spreads to the bones, lungs, brain, and liver. When it moves beyond the breast and nearby lymph nodes to distant parts of the body, it’s classified as stage 4 or metastatic breast cancer. Bone is the single most frequent destination, accounting for about 51% of first distant metastases, followed by the lungs (17%), brain (16%), and liver (6%). The remaining cases involve spread to multiple sites at once.
Lymph Nodes: The First Stop
Before breast cancer reaches distant organs, it typically travels through the lymphatic system. Lymph fluid from the breast drains into nearby lymph nodes under the arm (the axillary nodes) about 75% of the time. The remaining 25% drains into a combination of the axillary nodes and a set of nodes beneath the breastbone called the internal mammary nodes.
Surgeons often check a “sentinel node,” the first lymph node that fluid from the tumor drains into, to determine whether cancer has started to spread. About half the time, when cancer is found in a sentinel node, it hasn’t yet moved to any additional nodes. If it has, the likelihood of further spread depends on tumor size, how aggressive the cancer cells are, and whether they carry certain receptors like hormone receptors or HER2.
Bone Metastasis
Bone is the most common site of distant spread. Among patients diagnosed with metastatic breast cancer, roughly 65% have bone involvement, and in more than half of those cases, bone is the only site affected. The spine, pelvis, ribs, and long bones of the arms and legs are typical locations, because these areas have rich blood supplies that circulating cancer cells can easily reach.
Bone metastases can cause deep, persistent pain that worsens over time and doesn’t improve with rest. As cancer weakens the bone structure, it raises the risk of fractures from minor impacts or even normal activity. In the spine, growing tumors can compress the spinal cord, leading to numbness, weakness, or difficulty walking. Bone marrow can also be affected, which sometimes shows up as unexplained anemia or abnormal blood counts.
Lung Metastasis
The lungs are the second most common destination. Cancer cells can travel through the bloodstream and lodge in lung tissue, forming new tumors. Early lung metastases often produce no symptoms at all and are first spotted on routine imaging. As they grow, they can cause a persistent cough that doesn’t go away, shortness of breath during activities that used to feel easy, or chest pain. Some people notice they’re getting winded climbing stairs or walking distances they previously handled without trouble.
Brain Metastasis
Between 10% and 30% of people with metastatic breast cancer develop brain metastases at some point during their illness. This is one of the most concerning sites of spread because it can affect physical function, independence, personality, and quality of life.
Symptoms depend on where in the brain the tumors form. They can include persistent headaches (especially ones that are worse in the morning), seizures, vision changes, difficulty with balance or coordination, confusion, and personality shifts. Because the brain is protected by a barrier that limits which treatments can reach it, brain metastases can be particularly challenging to manage.
Liver Metastasis
When breast cancer spreads to the liver, it can disrupt the organ’s ability to filter toxins, produce proteins, and process nutrients. Early liver metastases may cause no obvious symptoms. As they progress, common signs include persistent fatigue, nausea, loss of appetite, unintentional weight loss, and a feeling of fullness or discomfort in the upper right abdomen. Yellowing of the skin and eyes (jaundice) can develop as liver function declines, and some patients develop fluid buildup in the abdomen.
How Cancer Subtype Affects Where It Spreads
Not all breast cancers behave the same way. The biological subtype of the tumor, determined by whether the cancer cells carry hormone receptors (estrogen or progesterone) and a protein called HER2, strongly influences which organs it favors.
- Hormone receptor-positive, HER2-negative: This is the most common subtype, and it overwhelmingly favors bone. About 59% of metastatic cases in this group involve bone as the primary site.
- Hormone receptor-positive, HER2-positive: Bone is still the top destination (47%), but liver metastases rise significantly compared to HER2-negative disease.
- Hormone receptor-negative, HER2-positive: This subtype has a notably high rate of liver metastasis (about 32%) and also carries a higher probability of brain involvement compared to other subtypes.
- Triple-negative: With no hormone receptors and no HER2, this aggressive subtype is more likely to spread to the lungs (32% of metastatic cases) and the brain. Up to half of people with metastatic triple-negative breast cancer develop brain metastases during their illness.
These patterns matter because they shape how doctors monitor for spread. Someone with a hormone receptor-positive tumor may be watched more closely for bone problems, while someone with triple-negative disease might get more frequent brain imaging.
How Spread Is Detected
Metastatic breast cancer is typically found through imaging of the chest, abdomen, and skeleton. The most commonly used tools are CT scans of the chest, abdomen, and pelvis, along with PET/CT scans, which can highlight areas of abnormal metabolic activity throughout the body. For bone-specific concerns, bone scans remain the standard first step, sometimes supplemented by CT or MRI to get a clearer picture of a specific area. MRI is particularly useful for evaluating potential brain metastases because of its detailed soft-tissue imaging.
These scans are used both to detect new spread and to track whether existing metastases are responding to treatment. How often you’re scanned depends on your subtype, symptoms, and treatment plan.
Survival With Metastatic Breast Cancer
The five-year relative survival rate for distant-stage breast cancer is 33%, according to American Cancer Society data. That means about one in three people with metastatic disease are alive five years after diagnosis. This number is an average across all subtypes and treatment approaches, and individual outcomes vary widely. Hormone receptor-positive cancers that spread only to bone, for example, tend to have a better prognosis than triple-negative cancers with brain or liver involvement.
Survival rates have been improving over time as newer targeted therapies, immunotherapies, and combination approaches become available. The 33% figure is based on data collected over previous years, so people diagnosed today may have better outcomes than that number suggests.