To plan the best treatment, your doctor needs to learn the extent (stage) of your thyroid cancer. Staging is a careful attempt to find out the size of the nodule, whether the cancer has spread, and if so, to what parts of the body.
Thyroid cancer spreads most often to the lymph nodes, lungs, and bones. When cancer spreads from its original place to another part of the body, the new tumor has the same kind of cancer cells and the same name as the original cancer. For example, if thyroid cancer spreads to the lungs, the cancer cells in the lungs are actually thyroid cancer cells. The disease is metastatic thyroid cancer, not lung cancer. For that reason, it’s treated as thyroid cancer, not lung cancer. Doctors call the new tumor “distant” or metastatic disease.