Solitary cystic nodal metastasis from occult papillary carcinoma of the thyroid mimicking a branchial cyst: a potential pitfall.

Thyroid carcinoma presenting as cervical lymph node metastasis with a clinically normal neck indicates an aggressive tumour of the thyroid. When the nodal metastasis is solitary and cystic, with no obvious suspicious thyroid mass on ultrasound (US) it may be mistaken for a branchial cyst. As the management of these two conditions is different, it is important to make a correct pre-operative diagnosis. We present the US features that help in distinguishing the two.