metastasis (meh-TAS-tuh-sis)

The spread of cancer from one part of the body to another. A tumor formed by cells that have spread is called a “metastatic tumor” or a “metastasis.” The metastatic tumor contains cells that are like those in the original (primary) tumor. The plural form of metastasis is metastases (meh-TAS-tuh-SEEZ).

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Metastasis; drawing shows primary cancer that has spread from the colon to other parts of the body (the lung and the brain). An inset shows cancer cells spreading from the primary cancer, through the blood and lymph system, to another part of the body where a metastatic tumor has formed.