There are several methods for describing the different thyroid cancer stages, but the tumor, node and metastasis (TNM) system is most common. T stages, which are based on the size of the primary tumor, range from 1 to 4 with 4 being the largest. N stages refer to whether the cancer has spread to the lymph nodes, while M stages describe whether the cancer has spread elsewhere within the body.
Thyroid cancer stages are mainly used to describe how far the cancer has spread. This is essential, because the farther the cancer has spread, the more aggressive the treatment needs to be. There are a number of ways to assess cancer development, but thyroid cancer stages are usually measured using the TNM system.
The T in TNM is based on a measure of the size of the main tumor. In most cases, the thyroid tumor will be given a rating from 1 to 4, with T1 being the smallest and T4 being the largest. To qualify as a T3 or T4 tumor, the growth must have expanded into the surrounding tissues.
N stages of thyroid cancer signify whether any lymph nodes in the body have cancer cells within them. The stages are simpler than T stages, because there are only two variations. If a patient has what is known as N0 thyroid cancer, then cancerous cells have not spread to the lymph nodes. When the cancer has spread to lymph nodes, the patient is said to have N1 thyroid cancer. Sometimes, the N1 stage is split into two stages — N1a and N1b — for when the cancer is only on one side of the neck or on both sides, respectively.
As with N stages, there also are two possible M stages. If the cancer has spread to other parts of the body, then it is known as M1. If it hasn’t, then it’s called M2 thyroid cancer. In general, the more the cancer has spread, the more difficult it is to treat, which is why the TNM rating system is important.
Treatment during the various thyroid cancer stages depends on how far the cancer has spread. Doctors use a variety of tests to check whether the cancer has spread and decide which treatment is most likely to be effective. There are other systems used for describing thyroid cancer stages, such as the number stages used in some other cancer measurements, but these are less common and depend on the exact type of thyroid cancer.