Branchial cleft cyst as the initial impression of a metastatic thyroid papillary carcinoma: two case reports.

Branchial cleft cysts are the most common lesions in lateral neck cysts, predominantly occurring in the fourth decade of life and without sexual propensity. Rare branchial cleft cysts are associated with malignant tumors metastatic from the oral cavity, nasal cavity, pharynx or thyroid gland. Occult thyroid papillary carcinomas often present as a solid mass in the lateral neck, with only a few cases revealing a branchial cleft cyst as the initial manifestation. Herein, we report two cases of metastatic thyroid papillary carcinoma that presented as lateral neck cysts, with preoperative diagnosis of branchial cleft cyst. Finally, after complete surgical resection and histopathologic examination, one case was diagnosed as cystic change of metastatic lymph node from thyroid papillary carcinoma, and the other was determined to be a branchial cleft cyst with concurrent lymph node metastasis from thyroid papillary carcinoma. When a branchial cleft cyst is diagnosed by clinical or histopathologic examination, a metastatic thyroid papillary carcinoma should be considered as part of the differential diagnosis.