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WHO Classification of Tumours
Follicular adenoma
Thyroid gland


A benign, encapsulated thyroid tumor with evidence for follicular cell differentiation that may be associated with thyroid hormone secretion. Follicular adenomas predominantly composed of oncocytic cells have been designated Hurthle cell adenoma . Several additional histological variants have been recognized
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Ronald A. DeLellis, Ricardo V. Lloyd, Philipp U. Heitz, Charis Eng
World Health Organization Classification of Tumours. Pathology and Genetics of Tumors of Endocrine Organs
IARC Press: Lyon 2004


The epidemiology of follicular adenoma is difficult to analyse because of the lack of consistent criteria for distinguishing hyperplastic nodules and adenomas. Solitary cold thyroid nodules occur in 47% of adults in an iodine sufficient area

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Klonoff DC, Greenspan FS (1982)
The thyroid nodule.
Adv Intern Med 27: 101-26

; in iodine deficient areas, the incidence of nodules, usually multiple, can rise to 50% of the population. Females are more commonly affected than males. Radiation-induced adenomas show a very long mean latent period
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Shore RE, Hildreth N, Dvoretsky P, Pasternack B, Andresen E (1993)
Benign thyroid adenomas among persons X-irradiated in infancy for enlarged thymus glands.
Radiat Res 134: 217-23