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Thyroid Cancer: Types And Their TNM Staging Classification


Thyroid cancer staging helps to determine the disease prognosis, and to select an appropriate treatment strategy.

TNM is the most commonly used staging system for the thyroid cancer. The system uses mainly 3 parameters to estimate the overall stage of a disease: “T” stands for “Tumor Size”; “N” for “Lymph Nodes”; and “M” for “Metastasis”. Numbers and/or letters after T (1, 2, 3a, 3b, 4a, and 4b), N (0, 1, 1a, and 1b), and M (0 and 1) provide more details about each of these parameters.

Once T, N, and M are determined through different diagnostic techniques, this information is combined to assign an overall stage (from 0 to IV) to the disease. In case of thyroid cancer, the overall disease prognosis and treatment depends on the type of cancer, and thus, different factors (apart from TNM) determine the overall stage for different types of thyroid cancer.

Following tables describe the characteristics of thyroid cancers (Differentiated, Medullary, and Anaplastic) according to different stages:

Differentiated Thyroid Carcinoma

Apart from the TNM scoring, age at diagnosis is also considered for assigning an overall stage to DTCs.

STAGE AGE AT DIAGNOSIS (YEARS) TNM DESCRIPTION
I <55 Any T Any N M0 Cancer of any size that might or might not has spread to nearby lymph nodes but no spread to distant body parts.
>/=55 T1-2 N0 M0 Cancer </=4 cm in size that is confined to the thyroid gland. No spread to nearby lymph nodes or distant body parts.
II <55 Any T Any N M1 Cancer of any size that might or might not has spread to nearby lymph nodes but has spread to distant body parts.
>/=55 T1-2 N1 M0 Cancer </=4 cm in size that is confined to the thyroid gland. Cancer has spread to nearby lymph nodes but has not spread to distant body parts.
T3a-3b Any N M0 Cancer >4 cm in size that is confined to the thyroid gland or it may have invaded into the strap muscles around the thyroid gland. Cancer might or might not has spread to nearby lymph nodes but has not spread to distant body parts.
III >/=55 Years T4a Any N M0 Cancer of any size that has invaded into the nearby tissues of the neck like the larynx (voice box), trachea (windpipe), esophagus (food-pipe), or the recurrent laryngeal nerve. Cancer might or might not have spread to nearby lymph nodes but has not spread to distant body parts.
IVA >/=55 Years T4b Any N M0 Cancer of any size that has invaded into the important nearby structures like the spine or large blood vessels. Cancer might or might not have spread to nearby lymph nodes but has not spread to distant body parts.
IVB >/=55 Years Any T Any N M1 Cancer of any size that might or might not have spread to nearby lymph nodes but have spread to distant body parts like distant lymph nodes, lungs, bones, etc.

Medullary Thyroid Carcinoma (MTC)

Age at diagnosis is not considered for the staging of MTCs

STAGE TNM DESCRIPTION
I T1-2 N0 M0 Cancer </=4 cm in size that is confined to the thyroid gland. No spread to nearby lymph nodes or distant body parts.
II T2-3 N0 M0 Cancer </=4 cm in size that is confined to the thyroid gland or cancer >4 cm in size that has invaded into the strap muscles around the thyroid gland. No spread to nearby lymph nodes or distant body parts.
III T1-3 N1a M0 Cancer </= 4 cm in size that is confined to the thyroid gland or cancer >4 cm in size that has invaded into the strap muscles around the thyroid gland. Cancer has spread to nearby lymph nodes in the neck region but has not spread to distant body parts.
IVA T4a Any N M0 Cancer of any size that has invaded into the nearby tissues of the neck like the larynx (voice box), trachea (windpipe), esophagus (food-pipe), or the recurrent laryngeal nerve. Cancer might or might not has spread to nearby lymph nodes but has not spread to distant body parts.
T1-3 N1b M0 Cancer </= 4 cm in size that is confined to the thyroid gland or cancer >4 cm in size that has invaded into the strap muscles around the thyroid gland. Cancer has spread to nearby lymph nodes in the neck (cervical or jugular nodes) but has not spread to distant body parts.
IVB T4b Any N M0 Cancer of any size that has invaded into the important nearby structures like the spine or large blood vessels. Cancer might or might not has spread to nearby lymph nodes but has not spread to distant body parts.
IVC Any T Any N M1 Cancer of any size that might or might not have spread to nearby lymph nodes but has spread to distant body parts like distant lymph nodes, lungs, bones, brain etc.

Anaplastic (Undifferentiated) Thyroid Cancer

Due to the aggressive nature of the anaplastic thyroid cancers, all such cancers are considered as stage IV disease.

STAGE TNM DESCRIPTION
IVA T1-3a N0 M0 Cancer of any size that is confined to the thyroid gland. No spread to nearby lymph nodes or distant body parts.
IVB T1-3a N1 M0 Cancer of any size that is confined to the thyroid gland. Cancer has spread to nearby lymph nodes in the neck region but has not spread to distant body parts.
T3b Any N M0 Cancer >4 cm in size that has invaded into the strap muscles around the thyroid gland. Cancer might or might not has spread to nearby lymph nodes but has not spread to distant body parts.
T4 Any N M0 Cancer of any size that has invaded into the nearby tissues of the neck like the larynx (voice box), trachea (windpipe), esophagus (food-pipe), recurrent laryngeal nerve, spine, or large blood vessels. Cancer might or might not has spread to nearby lymph nodes but has not spread to distant body parts.
IVC Any T Any N M1 Cancer of any size that might or might not have spread to nearby lymph nodes but has spread to distant body parts like distant lymph nodes, lungs, bones, brain etc.
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