Inflammatory Lesions and Lymphoma
Thyroiditis comprises a diverse group of inflammatory thyroid lesions and is one of the most common endocrine disorders in clinical practice. The most frequently encountered form is chronic lymphocytic thyroiditis (Hashimoto thyroiditis), first described in 1912, and a major cause of goiter and hypothyroidism in the United States. Clinically, patients are typically young to middle-aged women who present with a moderately enlarged nodular thyroid that is nontender. Approximately 90% of patients have high circulating antibody titers to thyroid peroxidase and, to a lesser extent, to thyroglobulin. Hashimoto thyroiditis is an auto-immune disorder that is thought to be caused by a derangement of suppressor T lymphocytes. Possible contributing factors to this disease include genetic associations with HLA-DR3, HLA-DR5, and HLA-B8; viral and infectious factors have also been proposed. Approximately 10% of cases are the fibrosing variant of Hashimoto thyroiditis that presents as severe hypothyroidism in elderly patients. Individuals with Hashimoto thyroiditis have a significantly increased relative risk of developing malignant lymphoma, and data suggest that there is also an increased risk of papillary carcinoma. Fine needle aspiration (FNA) is most often used to evaluate Hashimoto thyroiditis when a dominant nodule is present. Together with confirmatory antibody studies, FNA is an accurate means of diagnosing chronic lymphocytic thyroiditis.
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