Thyroid cancer

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PDQ Cancer Information Summaries . Bethesda (MD): National Cancer Institute (US); 2002-.


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This PDQ cancer information summary for health professionals provides comprehensive, peer-reviewed, evidence-based information about the treatment of adult thyroid cancer. It is intended as a resource khổng lồ inform và assist clinicians in the care of their patients. It does not provide formal guidelines or recommendations for making health care decisions.

This summary is reviewed regularly và updated as necessary by the PDQ Adult Treatment Editorial Board, which is editorially independent of the National Cancer Institute (NCI). The summary reflects an independent reviews of the literature and does not represent a policy statement of NCI or the National Institutes of Health (NIH).


General Information About Thyroid Cancer

Thyroid cancer includes the following four main types:


Papillary.
Follicular.
Medullary.
Anaplastic.

For clinical management ofthe patient, thyroid cancer is generally divided into the following two categories:<1>


Differentiated thyroid cancer, which includes well-differentiated tumors, poorly differentiated tumors, and undifferentiated tumors (papillary, follicular, or anaplastic).
Medullary thyroid cancer.

Well-differentiated tumors (papillary and follicular thyroid cancer) are highly treatable and usually curable. Poorly differentiated và undifferentiated thyroid tumors (anaplastic thyroid cancer) are less common, aggressive, metastasize early, & have a poorer prognosis. Medullary thyroid cancer is a neuroendocrine cancer that has an intermediate prognosis.

Thethyroid gland may occasionally be the site of other primary tumors, includingsarcomas, lymphomas, epidermoid carcinomas, & teratomas. The thyroid may also be the siteof metastasis from other cancers, particularly of the lung, breast, và kidney.


Incidence & Mortality

Estimated new cases và deaths from thyroid cancer in the United States in 2022:<2>


New cases: 43,800.
Deaths: 2,230.

Thyroidcancer affects women more often than men và usually occurs inpeople aged 25 to lớn 65 years. The incidence of this malignancy hasbeen increasing over the last decade. Thyroid cancer commonly presentsas a so-called cold nodule. It is detected as a palpable thyroid gland during a physical exam & evaluated with iodine I 131 scans; scintigraphy shows that the isotope is not taken up in an area of the gland. The overall incidence of cancer in a cold nodule is 12% to15%, but it is higher in people younger than 40 years and in people with calcifications present on preoperative ultrasonography.<3,4>


Anatomy

Thyroid gland tissue envelops the upper trachea just below the thyroid & cricoid cartilages that make up the larynx. The gland has an isthmus & often asymmetric right và left lobes; usually four parathyroid glands lie posteriorly. When swallowing, the thyroid may be felt to lớn rise with the larynx—most commonly in the presence of a disease process.


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Anatomy of the thyroid & parathyroid glands.


Risk Factors

Patients with a history of radiation therapy administered in infancy or childhood forbenign conditions of the head and neck (such asenlarged thymus, tonsils, or adenoids; or acne) have an increased risk of cancer andother abnormalities of the thyroid gland. In this group of patients,malignancies of the thyroid gland appear as early as 5 yearsafter radiation therapy and may appear 20 or more years later.<5> Radiation exposure as a consequence of nuclear fallout has also been associated with a high risk of thyroid cancer, especially in children.<6-8>

Other riskfactors for thyroid cancer include the following:<9>


Family history of thyroid disease or multiple endocrine neoplasia (MEN) syndrome.
A history of goiter.
Female gender.
Asian race.

Diagnostic & Staging Evaluation

The following tests và procedures may be used in the diagnosis & staging of thyroid cancer:


Physical exam và history.
Laryngoscopy.
Blood hooc môn studies.

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Blood chemistry studies.
Ultrasound exam.
Computed tomography scan.
Fine-needle aspiration biopsy of the thyroid.
Surgical excision.

Prognostic Factors for Well-Differentiated Thyroid Cancer

Age appears to be thesingle most important prognostic factor.<11> The prognosis for differentiatedcarcinoma (papillary or follicular) withoutextracapsular extension or vascular invasion is better for patients younger than 40 years.<11-15>

Patients considered at low risk according khổng lồ age, metastases, extent, and form size risk criteria include women younger than 50 years & men youngerthan 40 years without evidence of distant metastases. The low-risk group also includes older patients with primary papillary tumors smaller than 5cm without evidence of gross extrathyroidalinvasion, và older patients with follicular cancer without major capsular invasion or bloodvessel invasion.<13> Using these criteria, a retrospective study of 1,019patients showed that the 20-year survival rate was 98% for low-risk patients and50% for high-risk patients.<13>

Aretrospective surgical series of 931 previously untreated patients withdifferentiated thyroid cancer found that age older than 45 years, follicular histology, primary tumor larger than 4cm (T2–T3), extrathyroidal extension (T4), và distant metastases were adverse prognostic factors.<16,17> Favorable prognostic factors included female gender, multifocality, andregional lymph node involvement.<16> Other studies, however, have shown that regional lymph node involvement had noeffect <18,19> or had an adverse effect on survival.<14,15,20>

Another retrospective series of 1,807 patients found that the presence of distant metastases was most predictive of survival, followed by age.<21> An age cutoff of 55 years was identified as most predictive of survival. This led lớn an international multi-institutional validation of age 55 years as a cutoff for risk stratification in the American Joint Committee on Cancer/Union for International Cancer Control (AJCC/UICC) staging system for well-differentiated thyroid cancer. This analysis of 9,484 patients was responsible for the change in age cutoff from 45 years khổng lồ 55 years in the AJCC Cancer Staging Manual, 8th edition, using AJCC/UICC staging for well-differentiated thyroid cancer.<22>

The prognostic significance of lymph node status is controversial. Use of sentinel lymph node biopsy may aid in identifying patients with occult metastases who might benefit from central neck dissection.<23>

Diffuse, intenseimmunostaining for vascular endothelial growth factor in patients withpapillary cancer has been associated with a high rate of local recurrence anddistant metastases.<24> An elevated serum thyroglobulin màn chơi correlatesstrongly with recurrent tumor when found in patients with differentiatedthyroid cancer during postoperative evaluations.<25,26> Serum thyroglobulinlevels are most sensitive when patients are hypothyroid và have elevated serumthyroid-stimulating hooc môn levels.<27> Expression of the tumor suppressorgene p53 has also been associated with an adverse prognosis for patients withthyroid cancer.<28>

(Refer to the Clinical Features và Prognosis section of the Medullary Thyroid Cancer section and the Clinical Features and Prognosis section of the Anaplastic Thyroid Cancer section of this summary for more information about prognosis.)


Related Summaries

Other PDQ summaries containing information related lớn thyroid cancer include the following:


LiVolsi VA: Pathology of thyroid disease. In: Falk SA: Thyroid Disease: Endocrinology, Surgery, Nuclear Medicine, và Radiotherapy. Lippincott-Raven, 1997, pp 127-175.
Carling T, Udelsman R: Thyroid tumors. In: DeVita VT Jr, Lawrence TS, Rosenberg SA: Cancer: Principles & Practice of Oncology. 9th ed. Lippincott Williams & Wilkins, 2011, pp 1457-72.
van Herle AJ, van Herle KA: Thyroglobulin in benign and malignant thyroid disease. In: Falk SA: Thyroid Disease: Endocrinology, Surgery, Nuclear Medicine, và Radiotherapy. Lippincott-Raven, 1997, pp 601-618.