An unusual presentation of thyroid cancer.

Well-differentiated thyroid cancers can present with nodal metastasis that have undergone cystic degeneration. Rarely, mediastinal nodes may undergo cystic changes and pose a diagnostic dilemma, especially if the primary lesion is occult. We describe the case of a patient who presented with a large mediastinal cystic lesion which turned out to be metastasis from thyroid cancer.