131I and 124I Accumulation in a Thymic Cyst: Reply.

To the Editor: W e thank Dr Zanotti-Fregonara and Dr Hindie for the substantial comments and important questions raised regarding our previously published article about a woman with a history of papillary thyroid carcinoma and successful resection of a thymic cyst as the cause for a false-positive 131I scan. In this case report, we used TTF-1 to rule out thyroid origin of the resected cyst and CK5, 6, and 7 to support the diagnosis of a thymic cyst. We agree that immunohistochemistry analysis of thyroglobulin (Tg) might prove helpful to further elucidate