Metastasis occurs when cancer cells detach from their original tumor and travel to new locations in the body to form secondary tumors. When breast cancer metastasizes, it means the cancer cells have spread beyond the breast tissue where they first developed to other distant organs. This spread indicates a more advanced stage of the disease, often referred to as Stage IV breast cancer.
How Breast Cancer Spreads
Breast cancer cells can spread by detaching from the primary tumor. Once separated, these cells can enter the body’s circulatory systems, primarily the lymphatic system and the bloodstream. The lymphatic system, a network of vessels and nodes that carry lymph fluid, often serves as an initial pathway for cancer cells to travel from the breast.
Cancer cells can also directly enter the bloodstream, which then transports them throughout the body. Once they arrive at a new site, these cells can establish themselves and begin to grow, forming new tumors.
Common Metastasis Locations
Breast cancer can spread to various parts of the body, but certain organs are more frequently affected. The bones are a common site for breast cancer to metastasize, with approximately 70% of individuals with metastatic breast cancer experiencing bone metastasis. This is partly due to the rich blood supply within bone marrow, which provides a favorable environment for cancer cells to settle and grow. Specific bones often affected include the spine, ribs, pelvis, and the long bones of the arms and legs.
The lungs are another frequent destination for metastatic breast cancer, with about 60% of metastatic breast cancer patients experiencing lung metastasis. Cancer cells can travel through the bloodstream to the lungs, where they can form new tumors. These secondary tumors in the lungs often appear as multiple small areas rather than a single large mass.
The liver is also a common site for breast cancer to spread, with around 50% of patients developing liver metastases. The liver’s role in filtering blood makes it susceptible to receiving circulating cancer cells.
Brain metastasis is another potential, though less common, location for breast cancer spread, particularly with certain subtypes like triple-negative and HER2-positive breast cancers. Although it occurs less frequently than bone, lung, or liver metastasis, it remains a significant concern. Invasive ductal carcinoma (IDC), which accounts for about 85% of breast cancer cases, commonly spreads to the bones, lungs, liver, and brain.
Less common sites of metastasis include:
The skin
Distant lymph nodes
The female reproductive tract (ovaries, cervix, endometrium)
The digestive tract (esophagus, stomach, colon)
The pancreas
The kidneys
The thyroid
Recognizing Signs of Spread
When breast cancer metastasizes to different organs, it can cause a variety of symptoms depending on the affected area. For instance, if the cancer spreads to the bones, individuals may experience severe and persistent bone pain that progressively worsens, especially in the spine, ribs, pelvis, or long bones. This can also lead to weakened bones and, in some cases, pathological fractures.
Lung metastasis can manifest as a persistent dry cough, shortness of breath, and chest pain. These respiratory symptoms arise as the tumors interfere with normal lung function. When breast cancer spreads to the liver, symptoms may include pain or discomfort in the upper right side of the abdomen, sometimes radiating to the right shoulder. Other signs can involve nausea, loss of appetite, unintended weight loss, and jaundice, which is a yellowing of the skin and eyes.
If the brain is affected, symptoms can include persistent headaches that worsen over time, vision changes such as blurred or double vision, dizziness, seizures, and changes in behavior or personality. These symptoms stem from the tumors’ pressure or interference with brain function. It is important to note that these symptoms can be non-specific and may be caused by other conditions, necessitating medical evaluation for accurate diagnosis.
Detecting Metastatic Breast Cancer
Healthcare professionals employ several diagnostic methods to detect metastatic breast cancer. Imaging techniques are frequently used to visualize potential areas of spread throughout the body. These include computed tomography (CT) scans of the chest, abdomen, and pelvis, which provide detailed cross-sectional images to identify cancer in organs.
Magnetic resonance imaging (MRI) is particularly useful for detailed imaging of soft tissues like the brain and spinal cord, offering high-resolution views. Positron emission tomography (PET) scans, often combined with CT (PET/CT), use a radioactive tracer to highlight metabolically active cancer cells, helping to identify spread to various organs and soft tissues. Bone scans, which involve injecting a radioactive substance, are specifically used to detect bone metastases by identifying areas of increased bone activity.
While imaging provides strong indications, a biopsy of suspicious areas remains the most definitive method for confirming metastasis. During a biopsy, a small tissue sample is removed from the suspected metastatic site and examined under a microscope to confirm the presence of breast cancer cells. Blood tests, such as complete blood counts and liver function tests, may also offer clues, but they are not definitive for diagnosing metastatic disease on their own.