Esophageal 99mTc-pertechnetate uptake mimicking an autonomous thyroid adenoma in a patient with subacute thyroiditis: a case report.

Subacute thyroiditis (SAT) is one of the most common causes of thyrotoxicosis. Thyroid scans with radioiodine or technetium-99m pertechnetate (99mTc) are often performed in the workup of patients with thyrotoxicosis, particularly to differentiate between SAT and Graves's disease. Although very helpful, thyroid scans are prone to pitfalls that may occasionally lead to misdiagnosis. These pitfalls are largely related to physiologic uptake of radioiodine or 99mTc in non-thyroidal tissue, such as salivary gland and stomach that may result in false-positive findings. We present herein a very rare case of SAT misdiagnosed as an autonomous thyroid adenoma most likely due to focal 99mTc uptake in the esophagus. This case may have implications for the management of patients with suspected SAT, who undergo a radioiodine or 99mTc thyroid scan.