Andreas Vesalius (1514 -1564) first formally described the thyroid in his anatomy manuscript, De humani corporis Fabrica Libri septem. Since then, we have come a long way in understanding the anatomy, physiology, and workings of this endocrine gland. The thyroid gland is a midline structure in the neck. Derived from the primitive pharynx and neural crest cells, embryologically, the tissue mass divides, forming the isthmus and the two lateral lobes of the thyroid. Bu the age of 2, the gland is already half the adult size. Developmental anomalies could result in aberrant masses of ectopic thyroid tissue, cysts, and sinuses. Apart from that, the thyroid gland is no stranger to neoplastic lesions. Follicular lesions of the thyroid include many subvariants from the benign follicular adenoma right up to malignant follicular carcinomas, follicular variants of other malignant thyroid lesions.
Follicular adenomas are one subset of benign neoplasms that can occur in the thyroid gland or ectopic thyroid tissue. They typically present as a solitary thyroid nodule or in association with nodular hyperplasia or thyroiditis. Thyroid nodules are palpable in 4 to 7 % of individuals, but the prevalence of nodules detected incidentally by ultrasound shows a higher prevalence of 19 to 67 percent. The majority of thyroid nodules are asymptomatic. Similar to worldwide incidence, 60 to 70% of the US population present with thyroid nodules. Most of these are benign, although 5% exhibit malignant features. Although the distinguishing line between the adenoma itself and its malignant counterpart is tricky, this is for all practical purposes a benign neoplasm.
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