Cancer is an abnormal growth of previously healthy tissue, leading to the formation of a cancerous tumor. At the heart of cancer development are genetic mutations, which allow cells to continually divide, avoid cellular death and proliferate indefinitely to produce unlimited numbers of cancer cells. In its last stages, cancer cells gain migratory abilities, and can eventually prove fatal.
Lymph Node Invasion
In many cases, cancers initial spread to structures called lymph nodes. These nodes, located in several tissues throughout the body, normally house specialized white blood cells and help make up the immune system. During cancer development, tumor cells begin to migrate into and colonize the lymph nodes surrounding the tumor, a process called regional lymph node metastasis, according to the National Cancer Institute. The colonized lymph nodes become enlarged and matted together, and may lead to persistent pain around the swollen nodes. Upon diagnosis, doctors commonly check for cancer growth within lymph nodes surrounding the tumor to help assess the severity of the cancer.
Distant Metastasis
After colonizing lymph nodes around the tumor, the next stage of cancer development is often distant metastasis, or the colonization of distant tissues throughout the body. Cancer cells can travel around the body through the lymphatic system--cancer cells in the lymph nodes can enter lymph vessels and move around the body in lymphatic fluid. Alternatively, cancer cells can grow into blood vessels around the initial tumor, and travel in the bloodstream into distant organs. Finally, cancer can metastasize by migrating directly into another organ and forming a secondary tumor. Each type of cancer preferentially metastasizes to specific tissues--for example, prostate cancer most commonly spreads to bone tissue, according to the American Cancer Society. Upon diagnosing cancer, doctors will commonly perform body scans to look for other sites of cancer growth within the body.
The American Cancer Society indicates that most patients who die from cancer have developed some form of distant metastasis, and this distant cancer growth causes most cancer deaths.
Organ Damage and Failure
Once cancer cells have colonized and begun to grow in distant tissues, cancer patients experience progressive organ damage that can eventually lead to organ failure and death. Cancer cells often actively damage neighboring tissue, as this healthy tissue death provides more space for cancer growth. As a result, extensive cancer growth and the resulting extensive organ damage can lead to organ failure. In other cases, masses of cancer growth may inhibit organ functioning, such as blocking ducts within the liver, or blocking the flow of air into the lungs. Patients with metastatic cancer may receive therapies designed to slow organ damage or restore organ functioning to increase the patient's quality of life.
