Definition of Metastasis
Metastasis is the process by which cancer spreads from the place at which it first arose as a primary tumor to distant locations in the body.
Metastasis in Greek means displacement.
The term is used to denote the spread of a disease from one organ or part to another non-adjacent organ or part.
Malignant tumor cells and infections have the established capacity to metastasize. Until specified otherwise the term metastasis usually denotes malignant spread.
Why Does Metastasis Occur?
Cancer cells can break away, leak, or spill from a primary tumor, enter lymphatic and blood vessels, circulate through the bloodstream, and be deposited within normal tissue elsewhere in the body.
Metastasis is one of three hallmarks of malignant tumors.
Different tumors have different capacity to metastasize.
When tumor cells metastasize, the new tumor is called a secondary or metastatic tumor. This is done to differentiate it from original source or primary tumor.
However, the cells of new secondary tumor are similar to the primary tumor
How Does Metastasis Occur?
The spread of metastases may occur via the blood or the lymphatics or through both routes.
Metastasis is a complex series of steps in which cancer cells leave the original tumor site and migrate to other parts of the body via the bloodstream or the lymphatic system.
To do so, malignant cells break away from the primary tumor and attach to and degrade proteins that make up the surrounding extracellular matrix, which separates the tumor from adjoining tissue. By degrading these proteins, cancer cells are able to breach the extracellular matrix
The body resists metastasis by a variety of mechanisms through the actions of a class of proteins known as metastasis suppressors, of which about a dozen are known.
What Are The Places Where Metastases Occur?
The most common places for the metastases to occur are the lungs, liver, brain, and the bones. Different tumors behave differently in their predilection to sites for metastases
Common Sites Where Metastases Come From
- Skin: Melanoma*
*Other skin tumors rarely metastasize.
Metastases With Unknown Primary
Almost 10% of patients presenting to oncology units will have metastases without a primary tumor found.
These are termed as unknown or occult primaries and the patient is said to have cancer of unknown primary origin (CUP) or Unknown Primary Tumors (UPT).
Approximately, 3% of all cancers are of unknown primary origin. In some of these cases a primary tumor may appear later.
Symptoms of cancer metastasis depend location of the tumor.
- In lymph nodes, a common symptom is lymphadenopathy.
- Lungs: cough, hemoptysis and dyspnea (shortness of breath)
- Liver: hepatomegaly (enlarged liver)and jaundice.
- Bones: bone pain, fracture of affected bones.
- Brain: neurological symptoms such as headaches,seizures, and vertigo.
Although advanced cancer may cause pain, it is often not the first symptom.
Treatment and survival is determined by whether or not a cancer is local or has spread to other locations.
If the cancer spreads to other tissues and organs, it may decrease a patient’s likelihood of survival.
Radiosurgery, chemotherapy, radiation therapy, biological therapy, hormone therapy, surgery or a combination of these is used to.
The choice of treatment generally depends on the type of primary cancer, the size and location of the metastasis, the patient’s age and general health, and the types of treatments used previously.
The treatment options currently available are rarely able to cure metastatic cancer.
Text adapted from Wikipedia