Thyroid cancer

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Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1] Michael Maddaleni, B.S.

Thyroid Cancer Main Page
Patient Information
Overview
Classification Papillary Thyroid Cancer Follicular Thyroid Cancer Medullary Thyroid Cancer Anaplastic Thyroid Cancer Thyroid Lymphoma
Causes
Differential diagnosis

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Diagnosis

History and Symptoms | Physical Examination | Staging | Laboratory tests | Electrocardiogram | X Rays | CT | MRI Echocardiography or Ultrasound | Other images | Alternative diagnostics

Treatment

Medical therapy | Surgical options | Primary prevention | Secondary prevention | Financial costs | Future therapies

Classification

Thyroid cancers can be classified according to their pathological characteristics. The following variants can be distinguished (distribution over various subtypes may show regional variation):

• Papillary thyroid cancer (75%, incl. mixed papillary/follicular)
• Follicular thyroid cancer (16%)
• Medullary thyroid cancer (5-7%)
• Anaplastic thyroid cancer (3%)
• Lymphoma (1%)
• Squamous cell carcinoma, sarcoma (0.5 - 2%)

Medullary thyroid cancer (MTC)

This form of thyroid carcinoma originates from the parafollicular cells (C cells), which produce the hormone calcitonin. While the increased serum concentration of calcitonin is not harmful, it is useful as a marker which can be tested in blood. A second marker, carcinoembryonic antigen (CEA), also produced by medullary thyroid carcinoma, is released into the blood and it is useful as a serum or blood tumor marker. In general measurement of serum CEA is less sensitive than serum calcitonin for detecting the presence of a tumor, but has less minute to minute variability and is therefore useful as an indicator of tumor mass.

The prognosis of MTC is poorer than that of follicular and papillary thyroid cancer when it has metastasized (spread) beyond the thyroid gland. Approximately 25% the cancer develops in families. When MTC occurs by itself it is termed familial MTC; when it coexists with tumors of the parathyroid gland and medullary component of the adrenal glands (pheochromocytoma) it is called multiple endocrine neoplasia type 2 (MEN2).

Clinical features of medullary thyroid carcinoma

The major clinical symptom of medullary thyroid carcinoma is diarrhea; occasionally a patient will have flushing episodes. Both occur particularly with liver metastasis. Occasionally, diarrhea or flushing will be the initial presenting complaint. The flushing that occurs in medullary thyroid carcinoma is indistinguishable from that associated with carcinoid syndrome. The presumed cause of flushing and diarrhea is the excessive production of calcitonin gene products (calcitonin or calcitonin gene-related peptide) and differs from the causation of flushing and diarrhea in carcinoid syndrome. Sites of spread of medullary thyroid carcinoma include local lymph nodes in the neck, lymph nodes in the central portion of the chest (mediastinum), liver, lung, and bone. Spread to other sites such as skin or brain occurs but is uncommon.

Adjuvant therapy for medullary thyroid cancer

Unlike differentiated thyroid carcinoma, there is no role for radioiodine treatment in medullary-type disease. External beam radiotherapy should be considered for patients at high risk of regional recurrence, even after optimum surgical treatment. Brierley et al., conducted a retrospective study of the treatment given to patients with microscopic residual disease, extraglandular invasion, or lymph-node metastases and found the locoregional relapse-free rate at 10 years was 86%, compared with 52% for those patients who did not receive adjuvant therapy. Typically, 40 Gy is given in 20 fractions to the cervical, supraclavicular, and upper mediastinal lymph nodes for 4 weeks, with subsequent booster doses of 10 Gy in five fractions to the thyroid bed, especially in the setting of gross residual disease.

After a long period during which surgery and radiation therapy formed the major treatments for medullary thyroid carcinoma, clinical trials of several new tyrosine kinase inhibitors [3] are now being studied. Preliminary results show clear evidence of response of a small percentage of patients, providing hope for future advances.

Anaplastic thyroid cancer

This form of thyroid cancer has a very poor prognosis (near 100% mortality) due to its aggressive behavior and resistance to cancer treatments. It rapidly invades surrounding tissues (such as the trachea). The presence of regional lymphadenopathy in older patients in whom FNA reveals characteristic vesicular appearance of the nuclei would support a diagnosis of anaplastic carcinoma.

References

• Bennedbæk F.N.; Perrild H.; Hegedüs L. (1999). "Diagnosis and treatment of the solitary thyroid nodule. Results of a European survey". Clinical Endocrinology. 50 (3): 357–363.CS1 maint: Multiple names: authors list (link)
• Carlo Ravetto, Luigia Colombo, Massimo E. Dottorini (2000). "Usefulness of fine-needle aspiration in the diagnosis of thyroid carcinoma". Cancer Cytopathology. 90 (6): 357–363.CS1 maint: Multiple names: authors list (link)
• Jacques Barbet, Loïc Campion, Françoise Kraeber-Bodéré, Jean-François Chatal, and the GTE Study Group (2005). "Prognostic Impact of Serum Calcitonin and Carcinoembryonic Antigen Doubling-Times in Patients with Medullary Thyroid Carcinoma". The Journal of Clinical Endocrinology & Metabolism. 90 (11): 6077–6084.CS1 maint: Multiple names: authors list (link)

See also

• Chernobyl disaster (radioactive contamination is a cause of thyroid cancer)

External links

• Beth Israel Deaconess Medical Center: Thyroid cancer
• Template:Dmoz
• Thyroid Cancer Clinical Trials Page of the American Thyroid Association
• Nuclear Medicine Information =– Thyroid Diseases
• Thyroid Cancer- National Cancer Institute
• [4] - Thyroid Cancer Survivors' Association