Thyroid transcription factor 1 (TTF-1) and p63 expression in two primary thyroid papillary carcinomas of branchial cleft cysts.

Malignant lateral cervical cysts can be related to metastatic tumors or rarely to primary thyroid carcinoma arising in branchial cleft cysts. This study evaluates the expression of thyroid-associated transcription factor-1 (TTF-1) and p63 in three branchial cleft cysts and in two primary thyroid papillary carcinoma of branchial cleft cysts. TTF-1 was negative in the nuclei of the lining epithelia of branchial cleft cysts, but positive in the adjacent normal thyroid tissue, while TTF-1 was positive in the nuclei of the lining epithelia and in the nuclei of the papillae and follicles in branchial cleft cysts with ectopic thyroid carcinoma. P63 was positive in the nuclei of the lining epithelia of branchial cleft cysts, but negative in the adjacent normal thyroid tissue. Papillary thyroid carcinoma of branchial cleft cysts displayed p63-positive foci. In conclusion, our results demonstrate that TTF-1 cannot distinguish between primary and metastatic tumors of branchial cleft cysts. The detection of p63 in papillary thyroid carcinomas of branchial cleft cysts could suggest that p63 contributes to the onset of this tumor. It is really important to evaluate if the case has a metastatic derivation or represents papillary thyroid carcinoma arising in ectopic thyroid tissue in a branchial cleft cyst.