Autonomously functioning nodule arising from accessory mediastinal thyroid tissue.

Functional imaging using radionuclide Tc99m pertechnetate is routinely used in the evaluation of the problems related to the thyroid gland. Scintiscan has been useful in the visualization of thyroid tissue in ectopic sites due to congenital developmental anomalies. Similarly, the scan helps in establishing the diagnosis of autonomously functioning nodule when the nodule being evaluated appears "hot" with suppression of rest of the gland activity. Here, we present a very rare case of autonomously functioning thyroid adenoma in an ectopic focus of accessory thyroid tissue in the mediastinum.