Thyroid cancer begins in the thyroid gland. The American Cancer Society reports that there are different types of cells in the thyroid gland, and therefore there are different types of thyroid cancer, each with different stages of cancer progression.
Medullary Thyroid Cancer Stages
Medullary thyroid cancer develops in the thyroid's "C" cells. These cells are responsible for production of calcitonin, a hormone that regulates calcium levels in the blood. The National Cancer Institute reports that the staging of MTC starts with stage 0, meaning the cancerous cells have been found with a special screening but there is no tumor. In stage 1, the tumor is 2 cm or smaller, and remains only in the thyroid. Stage II finds the tumor has grown, but no larger than 4 cm, and it still remains in the thyroid. In stage III, the tumor may have grown larger than 4 cm, cancerous cells may be found in tissues outside, but near, the thyroid, or the cancer may have spread to lymph nodes that are close to the thyroid.
Stage IV contains three sub-classifications. Stage IV A the cancer has spread beyond the thyroid, and into the trachea, voice box, esophagus, or other nearby areas, and it may also be in the lymph nodes. At this stage, surgical removal of the cancer may still be possible. Stage IV B finds that the tumor cannot be surgically removed. The cancer has spread to the spinal column, carotid artery, blood vessels, and lymph nodes. In stage IV C, the cancer has progressed to other areas of the body, such as the lungs or liver.
Papillary and Follicular Thyroid Cancer Stages (under 45)
The stages for papillary and follicular thyroid cancer are different for those under 45 years of age, than for those over 45 years of age. According to the ACS, the reason for this is that those younger than 45 are much less likely to die from thyroid cancer.
For those under 45, stage I papillary cancer finds that the tumor can be any size, and cancerous cells may be in nearby lymph nodes and tissues, but the cancer has not progressed to other areas of the body. In stage II, the cancer is now in other parts, such as the liver, lungs, kidneys, or bones.
Papillary and Follicular Thyroid Cancer Stages (over 45)
Papillary and follicular thyroid cancer stages for those over 45 years of age are different, as there is greater risk. Here the staging is similar to medullary thyroid cancer. Stage I finds the tumor less than 2 cm, and it remains localized to the thyroid. In stage II, the tumor is larger than 2 cm, less than 4 cm, but still remains only in the thyroid. In stage III, the tumor can be any size, and has spread beyond the thyroid into nearby tissues. Cancerous cells may also have spread into nearby lymph nodes.
Stage IV, as in medullary cancer, has three sub-stages. In stage IV A, the tumor has grown beyond the thyroid to outside, nearby tissues, and possibly to lymph nodes on the sides of the neck. Stage IV B means that the thyroid cancer has spread to the spinal column, carotid artery and/or blood vessels near the lungs. Stage IV C indicates the papillary and follicular thyroid cancer is now found in other areas of the body.
Anaplastic Thyroid Cancer Stages
According to the American Cancer Society, anaplastic thyroid cancer is rare, and is thought to have developed from an existing papillary or follicular cancer. It is very aggressive and spreads quickly, which is why it is always classified as a stage IV cancer. There are three sub-stages however. Stage IV A finds the cancer in the thyroid and nearby lymph nodes, but it can still be removed by surgery. In stage IV B, the cancer is in nearby lymph nodes, the thyroid, but can not be taken out by surgery. In stage IV C, the cancer has now spread to several lymph nodes, as well as other areas of the body.
