Understanding Cancer Metastasis: Causes, Spread, and Treatment Options
How Cancer Spreads: Understanding Metastasis
Cancer begins when cells grow uncontrollably and become abnormal. The original site where cancer originates is referred to as the primary cancer or primary tumor. When cancer cells spread from their original location to other parts of the body, it is called metastatic cancer.
Metastatic cancer retains the same cell type and name as the primary tumor. Common sites of metastasis include the lungs, bones, liver, and brain. Treatment for metastatic cancer is typically based on the type, size, and location of the metastasis.
What is Primary Cancer?
Cancer can start in any organ or tissue of the body. The initial tumor is called the primary cancer or primary tumor, named after the body part or cell type where it originates.
What is Metastasis and How Does it Occur?
Metastasis refers to the spread of cancer cells from the primary tumor to other areas. These cells can detach and travel via the bloodstream or lymphatic system, which is responsible for producing and transporting infection-fighting cells.
When cancer cells establish a new tumor in another part of the body, this new growth is called a metastatic tumor. Importantly, the cells in this tumor are identical to those in the primary tumor. For example, if breast cancer spreads to the lungs, the tumor in the lung consists of breast cancer cells, not lung cancer cells. This condition is referred to as metastatic breast cancer.
Where Does Cancer Spread?
Cancer cells can potentially spread to almost any part of the body. They often first travel to nearby lymph nodes, referred to as regional lymph nodes, which is termed lymph node involvement or regional disease. When cancer reaches distant organs or faraway lymph nodes, it is called metastatic disease or distant disease.
The most common sites for metastasis from solid tumors are the lungs, bones, liver, and brain.
Certain cancers have specific patterns of spread:
Lung cancer often spreads to the brain or bones.
Colon cancer frequently metastasizes to the liver.
Prostate cancer tends to spread to bones.
Breast cancer commonly spreads to bones, lungs, liver, or brain.
Blood-related cancers such as leukemia, multiple myeloma, and lymphoma are usually widespread at diagnosis and are not classified as metastatic.
Symptoms of Metastatic Cancer
Not all patients with metastatic cancer experience symptoms. In some cases, metastases are detected incidentally through imaging tests performed for other reasons. Symptoms depend on the location and size of the metastasis. For example:
Bone metastases can cause pain and fractures.
Brain metastases may lead to headaches, seizures, or balance issues.
Lung metastases can cause shortness of breath.
Liver metastases may result in abdominal swelling or jaundice.
In some instances, symptoms of metastatic cancer can lead to the discovery of the primary tumor. For example, back pain caused by prostate cancer spreading to the pelvic bones may be the first indication of the disease.
Diagnosing Metastatic Cancer
To distinguish between a primary and metastatic tumor, a pathologist examines a sample under a microscope. Cancer cells typically resemble the cells of the tissue where the cancer started. Diagnostic tests can also identify markers or antigens that point to the primary cancer's origin.
Metastatic tumors can be found at the same time as the primary cancer or months to years later. In rare cases, the primary tumor cannot be identified despite extensive testing. This is referred to as cancer of unknown primary origin (CUP).
Treatment Options for Metastatic Cancer
Treatment for metastatic cancer may include:
Chemotherapy
Radiation therapy
Biological therapy
Hormone therapy
Surgery
Cryosurgery
Combination therapies
The choice of treatment depends on the type of primary cancer, the size and location of metastases, the patient’s overall health, and previous treatments. For cases of CUP, treatment can still be tailored to manage symptoms or control the disease.
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