Aetiological associations of malignant thyroid tumours
THE CONTEXT
Most thyroid cancers have no known aetiological factor. The passage identifies radiation exposure and several tumour-specific associations.
Radiation and papillary carcinoma
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Thyroid irradiation under 5 years of age is the most important identifiable aetiological factor in differentiated thyroid carcinoma, particularly papillary carcinoma.
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After the Chernobyl nuclear disaster, childhood thyroid cancer incidence in Gomel rose from less than 1 per million to 96 per million.
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Short-latency aggressive papillary thyroid carcinoma is associated with the ret/PTC3 oncogene. Later-developing cancers, which may be less aggressive, are associated with ret/PTC1.
Other tumour-specific associations
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Follicular carcinoma has a high incidence in endemic goitrous areas, possibly because of TSH stimulation.
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Malignant lymphomas sometimes develop in autoimmune thyroiditis. Lymphocytic infiltration during the autoimmune process may be an aetiological factor.