March 26, 2017
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Thyroid Cancer (cont.)

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What are thyroid nodules?

A thyroid nodule is an abnormal growth found within the thyroid gland. It may be solid, fluid filled (cystic) -- usually with a jelly like substance called colloid -- or a combination of both.

Most often nodules are found incidentally when the patient or health care professional feels the neck. Whether the nodule is benign or cancerous cannot necessarily be determined just by feeling it and further tests may be warranted.

What are the different types of thyroid cancer?

Thyroid cancers are classified based upon which cell type is involved.

Well differentiated cancers (in which thyroid cells are less abnormal looking) include:

  • Papillary thyroid cancer: This is the most common type of thyroid cancer. Papillary thyroid cancer accounts for 80% of cases.
  • Hürthle cell carcinoma: This is a rare variant of papillary cancer (also known as oncocytic carcinoma).
  • Follicular thyroid cancer: Follicular carcinoma is the second most common type of thyroid cancer. The follicular variety accounts for 10% of cases.
  • Medullary thyroid cancer: This thyroid cancer type arises from the C cells in the thyroid. Medullary thyroid cancers (MTCs) comprise 5% of all cases.
  • Anaplastic thyroid cancer: This rare cancer involves thyroid cells are very abnormal looking, accounting for 1% of all cases.
  • Lymphoma: This rare cancer is most often non-Hodgkin's B cell type.
  • Sarcoma: This type of thyroid cancer is very rare.

How do health care professionals diagnose thyroid cancer?

Once a lump in the thyroid is discovered, it is important to know whether it is benign or malignant (cancerous).

Often an ultrasound is performed to assess whether there is a single nodule or whether multiple nodules are present. Ultrasound can determine whether the nodule is fluid filled or solid. Ultrasound also can determine the general appearance of thyroid looking for inflammation or irregularities and the presence of enlarged lymph nodes nearby that may represent metastatic cancer.

Fine needle aspiration biopsy is the procedure performed to obtain a sample of cells from the nodule to determine if it is cancerous. Using ultrasound, a thin needle is placed into the nodule and cells from the nodule are obtained. These cells can be examined under a microscope by a pathologist to determine whether a cancer is present and if so, what type of cancer it is.

Results of the aspiration are usually reported as the following:

  • Malignant: risk of malignancy is 100%
  • Suspicious for malignancy: risk of malignancy is 50% to 75%
  • Follicular carcinoma: risk of malignancy is 20% to 30%
  • Atypical cells of unknown significance: risk of malignancy is 5%-10%
  • Benign: risk of malignancy is less than 1%

Sometimes, the results of the aspiration are unclear and indeterminate, and the aspiration may need to be repeated to get a better sample and more cells to study.

Another test involves ingesting radioactive iodine, which is taken up by the thyroid gland. The gland is scanned by a Geiger counter-type of apparatus that determines how much radioactive iodine has been taken up by the gland and any thyroid nodules. If the nodule picks up much of the iodine, it is referred to as a "hot nodule." Such nodules are rarely cancerous. Nodules that take up little to no iodine are referred to as "cold nodules." Although the overwhelming majority of such nodules are benign, 5% turn out to be malignant. Although thyroid scans may be helpful, aspiration of the gland is a much more useful test.

Blood tests may be ordered to determine thyroid hormone levels and levels of other hormones and electrolytes, like calcium, within the body. These tests indicate whether the cells of the thyroid produce too much or too little hormone, not if cancer is present.

On occasion CT, MRI, or PET scans may be useful in evaluating the neck structures if there is concern that thyroid cancer has spread (metastasis).

Medically Reviewed by a Doctor on 3/24/2017

Source: MedicineNet.com
http://www.medicinenet.com/thyroid_cancer/article.htm

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