Thyroid 'claw sign' a useful diagnostic marker in the outsized lesions of isthmus: A large colloid cyst.

Thyroid isthmus lesions are generally small sized and can be solid or cystic. Discerning isthmic origin of a large nodule, especially if purely cystic, can become a diagnostic challenge because of thin thyroid tissue in it. We report a case of a 68-year-old male patient who had 6 weeks history of non- inflammatory central neck swelling associated with recent dysphagia, for which he underwent ultrasound and computed tomography (CT) scan examinations. Colloid nodules usually do not require further attention. Despite being commonest and benign thyroid nodules, they may require treatment if causing pressure symptoms. Its imaging characteristics can be variable, but they usually exhibit comet tail artifacts on ultrasound. In equivocal cases, claw sign on CT scan is diagnostic to confirm the site. Radiologists have a principle role to rule out other differentials of cystic neck lesions by careful examination of imaging features. In our case, CT scan allowed to rule out primary differential of thyroglossal cyst and guided clinicians for specific management plan.