Cancer Cancer Basics

Cancer at a Distance: Understanding Metastasis

Medically Reviewed On: October 16, 2003

By Christine Haran

Twenty years ago, talking about cancer was so taboo that people were reluctant to even use the word. Today, due to increased awareness of cancer and improvements in detection and treatment, many people are living longer and feel more comfortable talking about their illness.

Still, the word "cancer" encompasses many different complex diseases and misunderstandings continue to arise. One common source of cancer confusion is the definition of metastastic cancer. Some wonder why a cousin is said to have died of breast cancer when it was actually a tumor in her lungs that lead to her death. In such cases, the primary, or original, tumor began in the breast. But then, cancer cells from that tumor broke off and traveled through the bloodstream to the lungs, where they established a metastastic tumor.

Thus, metastatic cancer refers to cancers that have spread to a site in the body that is far from the original tumor. Sometimes the person will experience symptoms such as pain—particularly when it seeds in bone—while other times it remains concealed and painless.

Below, Dr. Karen Antman, a professor of medicine and pharmacology at Columbia University College of Physicians and Surgeons and director of Columbia's Herbert Irving Comprehensive Cancer Center, explains how metastasis occurs, and treatments for some common metastases.

How would you define metastatic cancer?
Metastatic cancer occurs when the original (primary) tumor spreads to organs in other parts of the body. Some cancer cells break off from the tumor, travel through the blood stream or lymphatic system to another part of the body and invade and then the cells begin to multiply. And before traveling to distant sites in the body, cancer cells may also spread to the lymph nodes near the tumor.

What are some common sites of metastasis?
Cancer cells from much of the body often end up in the lungs, and metastases from within the abdomen often develop in the liver, because those are the first places that the blood passes through on it's way back to the heart. If the cancer cells are not trapped by the capillaries in the lung and liver, they will flow back to the heart and then out into the general circulation to other organs such as the bone, brain and skin.

How do doctors distinguish between primary and metastatic tumors?
Primary tumors in an organ usually resemble the cells in the organ. Metastatic tumors look somewhat like the organ in which the primary tumor developed. For example, a primary lung cancer, which arises in the bronchial ducts, looks different from a breast cancer that spreads to the lung. Also a primary cancer usually arises in a bronchial duct, whereas a metastatic tumor is found out in the air sacs.

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