Retrosternal Ectopic Thyroid Mimicking Esophagus in Tc-99m Pertechnetate Thyroid Scan

Area of Science:

• Nuclear Medicine
• Endocrinology
• Radiology

Background:

• Abnormal pertechnetate distribution can stem from various causes, including ectopic thyroid tissue and physiological uptake.
• Retrosternal ectopic thyroid tissue is often challenging to visualize on Technetium-99m (Tc-99m) scans due to sternal bone attenuation.

Purpose of the Study:

• To report a case of thyrotoxicosis with unusual pertechnetate uptake patterns.
• To demonstrate the utility of SPECT in localizing hyperfunctioning retrosternal ectopic thyroid tissue.

Main Methods:

• A patient with thyrotoxicosis presented with abnormal pertechnetate uptake mimicking esophageal activity.
• Water-drinking protocols were employed to differentiate physiological from abnormal uptake.
• Single-photon emission computed tomography (SPECT) was utilized for precise localization of the abnormal foci.

Main Results:

• Two abnormal foci of pertechnetate uptake were identified in the mediastinum, persisting after water consumption.
• SPECT imaging localized these foci to the retrosternal region, consistent with ectopic functioning thyroid tissue.
• The hyperfunctioning nature of the ectopic thyroid tissue allowed for its visualization despite sternal attenuation.

Conclusions:

• Hyperfunctioning retrosternal ectopic thyroid tissue can present with atypical pertechnetate distribution mimicking other conditions.
• SPECT imaging is crucial for accurately localizing ectopic thyroid tissue, especially when standard scans are inconclusive.
• This case highlights the importance of considering ectopic thyroid tissue in the differential diagnosis of abnormal mediastinal uptake.