Metastasize

Metastasis (pronounced meh-TAS-ta-sis) means the spread of cancer .Cancer cells can break away from a primary tumor, penetrate into lymphatic and blood vessels, circulate through the bloodstream,and grow in a new focus (metastasize) in normal tissues elsewhere in the body.

Tumors are classified as either benign or malignant.Malignant tumors can spread by invasion and metastasis while benign tumors cannot, hence grow only locally. By definition, theterm "cancer" applies only to malignant tumors.

Patients diagnosed with cancer want to know whether their disease is local or has spread to other locations. It is the abilityto spread to other tissues and organs that makes cancer a potentially life-threatening disease, so there is great interest inunderstanding what makes metastasis possible for a cancerous tumor.

When cancer cells spread to form a new tumor, it is called a secondary, or metastatic tumor, and its cellsare like those in the original tumor. This means, for example, that if breast cancer spreads (metastasizes) to the lung, thesecondary tumor is made up of abnormal breast cells (not abnormal lung cells). The disease in the lung is metastatic breastcancer (not lung cancer).

Cancer cells may spread to lymph nodes (regional lymph nodes) near theprimary tumor. This is called nodal involvement, positive nodes, or regional disease. Cancer cells can also spread to other partsof the body, distant from the primary tumor. Doctors use the term metastatic disease or distant disease to describe cancer thatspreads to other organs or to lymph nodes other than those near the primary tumor.

Factors involved in metastasis

Metastasis is a complex series of steps in which cancer cells leave the original tumor site and migrate to other parts of thebody via the bloodstream or lymph system. To do so, malignant cells break away from the primary tumor and attach to and degradeproteins that make up the surrounding extracellular matrix (ECM), which separates the tumor from adjoining tissue. By degrading these proteins, cancer cells are able to breach the ECM andescape. When oral cancers metastasize, they commonly travel through the lymphsystem to the lymph nodes in the neck.

Cancer researchers studying the conditions necessary for cancer metastasis have discovered that one of the critical eventsrequired is the growth of a new network of blood vessels. This process of forming new blood vessels is called angiogenesis .

Tumor angiogenesis is the proliferation of a network of blood vessels that penetrates into cancerous growths, supplying nutrients and oxygen andremoving waste products. Tumor angiogenesis actually starts with cancerous tumor cells releasing molecules that send signals tosurrounding normal host tissue. This signaling activates certain genes in the host tissue that, in turn, make proteins toencourage growth of new blood vessels.

Metastasis and primary cancer

Metastatis theoretically always coincides with a primary cancer. It is a tumor that started from a cancer cell or cells inanother part of the body. However, over 10% of patients presenting to oncology units will have metastases without aprimary tumour found. Studies have shown that if simple questioning does not reveal the cancer's source (coughing up blood-'probably lung', urinating blood - 'probably bladder'), complex imaging will not either. In some of these cases a primary willappear later.

The use of immunohistochemistry has permitted pathologists to give an identity to many of these metastases.Imaging of the indicated area only occasionally reveals a primary however.

Diagnosis of primary and secondary tumors

The cells in a metastatic tumor resemble those in the primary tumor. Once the cancerous tissue is examined under a microscopeto determine the cell type, a doctor can usually tell whether that type of cell is normally found in the part of the body fromwhich the tissue sample was taken.

For instance, breast cancer cells look the same whether they are found in the breast or have spread to another part of thebody. So, if a tissue sample taken from a tumor in the lung contains cells that look like breast cells, the doctor determinesthat the lung tumor is a secondary tumor.

Metastatic cancers may be found at the same time as the primary tumor, or months or years later. When a second tumor is foundin a patient who has been treated for cancer in the past, it is more often a metastasis than another primary tumor.

In about 10% of cancer patients, a secondary tumor is diagnosed, but no primary cancer can be found, in spite of extensivetests. Doctors refer to the primary tumor as unknown or occult, and the patient is said to have cancer of unknown primary origin(CUP). In rare cases (e.g. of melanoma ) no primary tumor is found even on autopsy.It is therefore thought that some primary tumors can regress completely, but leave their metastases behind.

Treatments for metastatic cancer

When cancer has metastasized, it may be treated with chemotherapy , radiation therapy , biological therapy , hormone therapy , surgery , or a combination of these. The choice of treatment generally depends on thetype of primary cancer, the size and location of the metastasis, the patient's age and general health, and the types oftreatments used previously. In patients diagnosed with CUP, it is still possible to treat the disease even when the primary tumorcannot be located.

External links

• What You Need to GetStarted Researching Your Options from CancerGuide