The original tumor is called the primary cancer or primary tumor and is usually named for the part of the body in which it begins. Metastatic cancer is cancer that has spread. Cancer cells can break away from a primary tumor and travel through the bloodstream or lymphatic system to other parts of the body. The cancer cells may build up in lymph nodes near the primary tumor, and they may travel to distant parts of the body. The spread of cancer cells is called metastasis.
Metastatic tumors are more likely to grow in some parts of the body than in others.
The lymph nodes, brain, lungs, liver, and bones are common sites of metastasis. A metastasis is a tumor that started from a cancer cell or cells in another part of the body. Sometimes, however, a primary cancer is discovered only after a metastasis causes symptoms. The cells in a metastatic tumor resemble those in the primary tumor. Once the cancerous tissue is examined under a microscope to determine the cell type, a doctor can usually tell whether that type of cell is normally found in the part of the body from which the tissue sample was taken.