The stage of a cancer describes its size and whether it has spread beyond the area of the body where it started. Staging systems are often updated to help doctors plan the best treatment and give an idea of what is likely to happen. This means they are becoming more detailed and complicated.
Different types of cancer are staged differently. The stages we describe here are about thyroid cancer. The most common staging system is the TNM system.
T describes the size of the tumour and whether it has spread into nearby tissues around the thyroid gland.
N describes whether the cancer has spread to the lymph nodes close to the thyroid gland.
M describes whether the cancer has spread to other parts of the body, such as the lungs or the bones (metastatic or secondary cancer).