Stages of Thyroid Cancer

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Thyroid is a butterfly-shaped endocrine gland located just below the larynx (voice box). It consists of 2 lobes that are present on either side of the trachea and are joined together by an isthmus present anterior to the trachea.

Most of the thyroid is made of follicular cells that form spherical sacs enveloping a colloid and secrete thyroid hormones – thyroxine and triiodothyronine, under the influence of thyroid stimulating hormone (TSH) secreted from the anterior pituitary. Thyroid hormones regulate body’s basal metabolic rate.

A few parafollicular or C-cells lie between the follicular cells in the thyroid gland and secrete calcitonin. Calcitonin is a hormone that helps in maintaining appropriate calcium level in the blood. Other, less common cells in the thyroid gland include lymphocytes, fibroblasts, and adipocytes.

Four parathyroid glands are present on the posterior surface of the two lobes of the thyroid gland. The parathyroid glands secrete parathormone that helps in maintaining an appropriate level of calcium, magnesium, and phosphate in the blood. Thyroid cancer is assessed to be the most frequently diagnosed endocrine cancer and twelfth most commonly diagnosed cancers in the United States (US).

Staging of Thyroid Cancer

Differentiated Thyroid Cancer

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

Stage I

Age at Diagnosis <55 years – 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.

Age at Diagnosis >/=55 years – 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.

Stage II

Age at Diagnosis <55 years – 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.

Age at Diagnosis >/=55 years – 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.

Stage III

Age at Diagnosis >/=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.

Stage IVA

Age at Diagnosis >/=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.

Stage IVB

Age at Diagnosis >/=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 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.

Stage 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.

Stage 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.

Stage 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.

Stage 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.

Stage 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 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.

Stage 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.

Stage 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.

Thyroid Cancer Staging Investigations

If a person is suspected to have thyroid cancer due to the presence of signs and symptoms, certain investigations are required to confirm the diagnosis of the disease and determining the stage of the disease, which in turn helps in choosing an appropriate treatment option. They help in distinguishing between benign thyroid disease (a benign nodule, goiter, or Grave’s disease) and thyroid cancer.

Thyroid ultrasound

thyroid ultrasound This technique may be used to-

  • examine the thyroid tissue for any abnormality
  • distinguish between fluid-filled cysts (mostly benign) and solid tumor masses (mostly cancerous)
  • reveal certain features of the cancerous nodules like micro-calcifications, irregular borders, or abnormal vascular patterns
  • Nearby lymph nodes (both in the lateral and the central neck) can also be studied for any sign of cancer spread with the help of this test.
  • guide a biopsy needle to collect biopsy samples from the affected area. This test does not use any ionizing radiation and is considered safe.

Blood Tests

Blood tests are not used to diagnose thyroid cancer itself but these tests can reveal certain important information that can provide direction to the diagnostic workup of thyroid cancer. Following are commonly employed blood test for this purpose.

Thyroid Hormone Level

thyroid hormone level The level of thyroid hormones – thyroxine and tri-iodothyronine, may be utilized to assess the functioning of the thyroid gland. The thyroid hormone level is usually normal in most thyroid cancers but may be elevated in the case of hyperfunctioning thyroid cancer and may require further investigations.

Thyroid Stimulating Hormone (TSH) Level

The TSH is secreted by the anterior pituitary and its level in the blood is regulated through negative feedback mechanism by thyroid hormones. Thus, an elevated level of TSH indicates diminished thyroid functioning while a suppressed TSH level indicates hyperfunctioning thyroid (or thyroid nodule).

The hyperfunctioning thyroid nodules are rarely cancerous and can be easily detected with the help of a radioiodine scan. No further investigation is generally required unless a cold nodule (an area in the thyroid with lower radioactivity then surrounding) is present. Cold nodules can be cancerous and thus require further investigation.

Calcitonin Level

calcitonin level Calcitonin is a hormone secreted by C-cells of the thyroid gland. These cells give rise to MTC that is usually associated with elevated levels of calcitonin. Thus, elevated calcitonin levels may signal MTC and should be handled appropriately.

Calcitonin level estimation may also be helpful in the assessment of the efficacy of the treatment/surgery for MTC (which generally cause calcitonin level to decrease) and the progression/recurrence of the disease in patients with MTC (indicated by increased calcitonin level after the decrease caused by the treatment).

Thyroglobulin Level

thyroglobulin test Thyroglobulin is a protein made by thyroid cells and its level in the blood usually remains normal in most thyroid cancers. However, levels of thyroglobulin can be helpful in assessing the efficacy of the treatment/surgery (that should bring down the thyroglobulin level) and the progression/recurrence of the disease in patients with DTC (if thyroglobulin level increases, which was diminished after treatment).

Carcinoembryonic antigen (CEA)

carcinoembryonic antigen- CEA test CEA is a protein (tumor marker) that is found to be elevated in many patients with thyroid cancer (especially MTC). Monitoring of the CEA level can be helpful in assessing the efficacy of the treatment/surgery (that should bring down the elevated CEA level) and the progression/recurrence of the disease in MTC patients who had high CEA levels before treatment.

Radioiodine (I-131) Scan

radioiodine-I 131 scan In this test, radioiodine (I-131) is first administered to a patient. Iodine is essential for making thyroid hormones by follicular cells of the thyroid gland. Thus, radioiodine is absorbed by the thyroid follicular cells including the thyroid cancer cells (papillary, follicular, or Hürthle cell). This absorption of radioiodine occurs under the influence of TSH, and thus, a higher TSH level is usually achieved by injecting thyrotropin (recombinant TSH) to the patient before radioiodine dosing.

The whole body is then scanned for the presence of radioiodine with the help of a radioactivity detector. Abnormal areas in thyroid gland with low radioactivity compared to the surrounding are known as ‘cold nodules’, while the areas with high radioactivity than surrounding are known as ‘hot nodules’.

Cold nodules can be cancerous and require further investigation while hot nodules are usually benign. This test is mostly utilized to assess the efficacy of a treatment/surgery and the spread/recurrence of the disease in patients with DTC. If cancer cells are detected on radioiodine scan after surgical removal of the thyroid gland, it indicates spread of disease and disease sensitive to radioiodine therapy.

Thyroid FNAC

thyroid fine needle aspiration This is a confirmatory test and considered as gold standard in establishing the diagnosis of thyroid cancer. Biopsy sample(s) is generally collected from the suspected areas or cold nodules observed during the thyroid ultrasound or radioiodine scan, respectively. A fine needle aspiration (FNA) biopsy technique is generally utilized for the diagnosis of thyroid cancer.

Sometimes, biopsy sample(s) from lymph nodes in the central or lateral neck region is also collected for examination. The collected biopsy samples are examined under the microscope in a laboratory and can provide very useful information such as the type of thyroid cancer, the severity of cancerous changes involved (level of differentiation), and the presence of specific defective genes or proteins in the cancer cells.

Imaging Tests

These tests are generally employed after the establishment of the pathological diagnosis. They help to detect the spread of disease to distant body parts and assess the stage of the disease so that an appropriate treatment option can be selected. Alternatively, these tests are employed after treatment to evaluate the treatment efficacy and to detect disease response, progression, or recurrence.

  • Computed tomography (CT) scan
  • Magnetic resonance imaging (MRI) scan
  • Positron emission tomography (PET) scan
  • Bone Scan

 

Read about Treatment of Thyroid Cancer here.

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