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ESSENTIALS OF DIAGNOSIS
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ESSENTIALS OF DIAGNOSIS
Painless swelling in region of thyroid.
Thyroid function tests are usually normal.
Possible history of childhood irradiation to head and neck region.
Positive thyroid FNA cytology.
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GENERAL CONSIDERATIONS
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Thyroid cancers historically were discovered by detection of a thyroid mass by a patient or provider. Over the last 40 years, small nonpalpable thyroid malignancies have been detected with increasing frequency as a result of the widespread use of ultrasound, CT, MRI, and PET imaging. While the yearly incidence of diagnosed thyroid malignancy in the United States has tripled during this period to about 44,000 cases annually, mortality from thyroid cancer has remained relatively stable, accounting for about 2400 deaths annually. Thyroid cancers are diagnosed three times more frequently in women than men. However, the mortality rate from thyroid cancer is nearly as high in men compared to women. Larger differentiated thyroid cancers (palpable or larger than 1 cm) are more likely to behave in a malignant fashion and usually require treatment.
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Of thyroid cancers that are detected incidentally on imaging, most are nonpalpable, small (smaller than 1 cm) papillary microcarcinomas. Although these microcarcinoma fufill pathologic criteria for malignancy, they are almost all indolent; as such, a new terminology has been proposed for them: “Indolent Lesion of Epithelial Origin (IDLE)”. In routine autopsy series, thyroid papillary microcarcinoma (smaller than 1 cm) is found with in 11.5% in both women and men.
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Four histologic types account for 97% of thyroid cancer: papillary, follicular, medullary, and anaplastic (Table 28–7).
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Pure papillary (and mixed papillary-follicular) carcinoma represents over 85% of all diagnosed thyroid cancers. It usually presents as a single thyroid nodule but can arise out of a multinodular goiter. Papillary thyroid carcinoma is commonly multifocal and involves both lobes in 30% of patients.
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Papillary thyroid carcinoma is the least aggressive thyroid malignancy. It tends to grow slowly and often remains confined to the thyroid and regional lymph nodes for years. In about 80% of patients, there are microscopic (smaller than 2 mm) metastases to cervical lymph nodes, which does not appear to affect survival. The malignancy may become more aggressive in patients over age 45 years, especially in older adults. The cancer may invade the trachea and local muscles and spread to the lungs. Papillary thyroid carcinoma is caused by genetic mutations ...