Thyroid hemiagenesis: report of a case and review of literature.

Our objective was to report an incidental finding of thyroid hemiagenesis in a patient who presented with a left neck mass, present a review of literature, and to discuss management of this diagnosis. Case report and review of literature. An internet-based literature search was performed via Pubmed with key words, "hemithyroid agenesis, thyroid hemiagenesis, absent thyroid gland". Clinical, pathological, radiologic data and follow up information is reported. A 55 year old woman with a left neck mass presented to our service. A diagnostic CT scan of the head and neck revealed an unrelated finding of an absent left thyroid lobe. A review of the CT imaging did not reveal ectopic thyroid tissue. A complete physical examination including a flexible laryngoscopy was unremarkable. The neck mass was pathologically a granulomatous lesion on surgical pathology. Thyroid function tests were within normal limits. In follow-up, patient remains asymptomatic. Hemithyroid agenesis is most commonly associated with hyperthyroidism, although, hypothyroidism has been reported. Pathology that can be associated in the remnant thyroid lobe includes adenocarcinoma, adenoma, multinodular goiter, and chronic thyroiditis. In counseling patients, it is important to educate them regarding these associated conditions and offer appropriate work up if indicated. Incidental thyroid agenesis with a negative work up can then be observed.