- Thyroid cancer
Thyroid cancer refers to any of four kinds of malignant
tumors of the thyroidgland: papillary, follicular, medullary or anaplastic. Papillary and follicular tumors are the most common. They grow slowly and may recur, but are generally not fatal in patients under 45 years of age. Medullary tumors have a good prognosis if restricted to the thyroid gland and a poorer prognosis if metastasisoccurs. Anaplastic tumors are fast-growing and respond poorly to therapy.
Thyroid nodules are diagnosed by ultrasound guided
fine needle aspiration(USG/FNA) or frequently by thyroidectomy(surgical removal and subsequent histological examination). As thyroid cancer can take up iodine, radioactive iodineis commonly used to treat thyroid carcinomas, followed by TSH suppression by thyroxinetherapy.
Most often the first symptom of thyroid cancer is a nodule in the thyroid region of the neck. However, many adults have small nodules in their thyroids. But typically under 5% of these nodules are found to be malignant. Sometimes the first sign is an enlarged lymph node. Later symptoms that can be present are pain in the anterior region of the neck and changes in voice.
Thyroid cancer is usually found in a
euthyroidpatient, but hyperthyroidismmay be a symptom of a large or metastatic well-differentiated tumor. Nodulesshould be of particular concern when they are found in children or those under the age of 20. The presentation of benign nodules at this age is less likely, and thus the potential for malignancy is far greater.
noduleis found during a physical examination, a referral to an endocrinologist, or a thyroidologistis the best approach. Most commonly an ultrasoundis performed to confirm the presence of a nodule, and assess the status of the whole gland. Measurement of thyroid stimulating hormoneand anti-thyroid antibodies will help decide if there is a functional thyroid disease such as Hashimoto's thyroiditispresent, a known cause of a benign nodular goiter. [cite journal |author=Bennedbaek FN, Perrild H, Hegedüs L |title=Diagnosis and treatment of the solitary thyroid nodule. Results of a European survey |journal=Clin. Endocrinol. (Oxf) |volume=50 |issue=3 |pages=357–63 |year=1999 |pmid=10435062 |doi=10.1046/j.1365-2265.1999.00663.x|url=http://www.blackwell-synergy.com/openurl?genre=article&sid=nlm:pubmed&issn=0300-0664&date=1999&volume=50&issue=3&spage=357]
Fine needle biopsy
One approach used to determine whether the nodule is malignant is the
fine needle biopsy(FNB) [cite journal |author=Ravetto C, Colombo L, Dottorini ME |title=Usefulness of fine-needle aspiration in the diagnosis of thyroid carcinoma: a retrospective study in 37,895 patients |journal=Cancer |volume=90 |issue=6 |pages=357–63 |year=2000 |pmid=11156519|doi=10.1002/1097-0142(20001225)90:6<357::AID-CNCR6>3.0.CO;2-4|url= ] , which some have described as the most cost-effective, sensitive and accurate test.Fact|date=December 2007 FNB or ultrasound-guided FNA usually yields sufficient thyroid cells to assess the risk of malignancy, although in some cases, the suspected nodule may need to be removed surgically for pathological examination.
Rarely, a biopsy is done using a large cutting needle, so that the a piece of nodule capsule can be obtained.
Blood or imaging tests may be done prior to or in lieu of a biopsy. The possibility of a nodule which secretes thyroid hormone (which is less likely to be cancer) or hypothyroidism is investigated by measuring
thyroid stimulating hormone(TSH), and the thyroid hormones thyroxine(T4) and triiodothyronine(T3).
Tests for serum thyroid autoantibodies are sometimes done as these may indicate
autoimmunethyroid disease (which can mimic nodular disease).
The blood assays may be accompanied by ultrasound imaging of the nodule to determine the position, size and texture, and to assess whether the nodule may be
cystic (fluid filled). Also suspicious findings in a nodule are hypoechoic,cite journal |author=Wong KT, Ahuja AT |title=Ultrasound of thyroid cancer |journal=Cancer Imaging |volume=5 |issue= |pages=157–66 |year=2005 |pmid=16361145 |doi=10.1102/1470-7330.2005.0110] irregular borders, microcalcifications, or very high levels of blood flow within the nodule. Less suspicious findings in benign nodules include, hyperechoic, comet tail artifacts from colloidClarifyme|date=September 2008, no blood flow in the nodule and a halo, or smooth border.
Some clinicians will also request
technetium(Tc) or radioactive iodine(I) imaging of the thyroidFact|date=September 2008. An 123I scan showing a hot nodule, accompanied by a lower than normal TSH, is strong evidence that the nodule is not cancerous.
Thyroid cancers can be classified according to their pathological characteristics.cite web |url=http://www.cancer.gov/cancertopics/pdq/treatment/thyroid/HealthProfessional/page2 |title=Thyroid Cancer Treatment - National Cancer Institute |accessdate=2007-12-22 |format= |work=] cite web |url=http://cancerweb.ncl.ac.uk/cancernet/101252.html#2_CELLULARCLASSIFICATION |title=Thyroid cancer |accessdate=2007-12-22 |format= |work=] The following variants can be distinguished (distribution over various subtypes may show regional variation):
Papillary thyroid cancer
Follicular thyroid cancer
Medullary thyroid cancer(up to 8%)cite journal |author=Schlumberger M, Carlomagno F, Baudin E, Bidart JM, Santoro M |title=New therapeutic approaches to treat medullary thyroid carcinoma |journal=Nat Clin Pract Endocrinol Metab |volume=4 |issue=1 |pages=22–32 |year=2008 |pmid=18084343 |doi=10.1038/ncpendmet0717]
Anaplastic thyroid cancer
Squamous cell carcinoma, sarcoma
The follicular and papillary types together can be classified as "differentiated thyroid cancer".cite journal |author=Nix P, Nicolaides A, Coatesworth AP |title=Thyroid cancer review 2: management of differentiated thyroid cancers |journal=Int. J. Clin. Pract. |volume=59 |issue=12 |pages=1459–63 |year=2005 |pmid=16351679 |doi=10.1111/j.1368-5031.2005.00672.x |url=http://www.medscape.com/viewarticle/518396] These types have a more favorable prognosis than the medullary and undifferentiated types.cite journal |author=Nix PA, Nicolaides A, Coatesworth AP |title=Thyroid cancer review 3: management of medullary and undifferentiated thyroid cancer |journal=Int. J. Clin. Pract. |volume=60 |issue=1 |pages=80–4 |year=2006 |pmid=16409432 |doi=10.1111/j.1742-1241.2005.00673.x |url=http://www.blackwell-synergy.com/openurl?genre=article&sid=nlm:pubmed&issn=1368-5031&date=2006&volume=60&issue=1&spage=80]
radioactive contamination(a cause of thyroid cancer)
* [http://www.thyroidtrials.org Thyroid Cancer Clinical Trials Page] of the American Thyroid Association
* [http://www.thyroidproblems.org/tumors.php Thyroid Tumors and Cancer - Thyroid Problems]
* [http://www.nucmedinfo.com/Pages/thyroid.html Nuclear Medicine Information =– Thyroid Diseases]
* [http://www.cancer.gov/cancertopics/types/thyroid Thyroid Cancer] - National Cancer Institute
* [http://www.thyca.org Thyroid Cancer Survivors' Association]
* [http://patients.uptodate.com/topic.asp?file=endocrin/11828 Diagnostic patient information]
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