What is metastasis?
Metastasis is a term used in pathology to describe the process by which cancer spreads from where it first started (the primary site) to other body parts. When cancer cells break away from the original tumor, they can travel through the bloodstream or the lymphatic system (a network of vessels and nodes that helps fight infection) to distant organs and tissues. This is called lymphovascular invasion. Once these cells reach a new location, they may grow and form new tumors, known as metastases, which are the same type of cancer as the original tumor. Although any body part may be involved, metastases are commonly found in lymph nodes, the liver, the lungs, and bones.
Metastasis is important for several reasons:
- It indicates the cancer is advancing: When cancer spreads, it means the disease is becoming more serious and may be harder to treat. The presence of metastasis often signifies a later stage of cancer.
- It can affect the body’s functioning: Metastatic tumors can interfere with organ function. For example, if cancer spreads to the liver, it can affect the liver’s ability to process substances in the body. If it spreads to the bones, it can cause pain and fractures.
- It guides treatment decisions: Knowing whether cancer has spread helps doctors decide on the best treatment approach. Cancers that have not spread might be treated with surgery to remove the tumor, but if there is metastasis, more systemic treatments like chemotherapy or targeted therapy might be needed to address cancer cells throughout the body.
- It affects prognosis: Generally, cancers that have spread have a more challenging prognosis than cancers that have not. The ability to control or cure the cancer depends on how much it has spread and where the new tumors are located.
What are common sites for metastasis?
Some types of cancer tend to spread to specific parts of the body.
Common sites for metastasis include:
- Lymph nodes: These small, bean-shaped structures are often the first place cancer cells spread.
- Liver: Many cancers, especially colon, pancreas, and stomach, often spread to the liver.
- Lungs: Lung metastases are common for cancers of the breast, colon, kidney, and bones.
- Bones: Cancers such as breast, prostate, and lung cancer can spread to the bones.
- Brain: Certain cancers, like lung cancer, melanoma, and breast cancer, may spread to the brain.
Not all cancers spread in the same way or to the same locations. The pattern of metastasis depends on the type of cancer and its specific characteristics.
How is this diagnosis made?
Metastasis is diagnosed through imaging tests, laboratory tests, and microscopic examination of tissue samples.
- Imaging tests: Techniques like CT scans, MRIs, PET scans, or bone scans are used to look for suspicious areas where cancer may have spread.
- Biopsy: If an abnormal area is found, a biopsy may be performed to remove a small piece of tissue. A pathologist examines the tissue under a microscope to determine if the cells are cancerous and similar to those in the primary tumour.
- Molecular and immunohistochemical tests: These tests can help confirm whether the tumour cells in a new location match the cancer cells in the primary tumour.