Abstract
A 79-year-old woman was admitted to the hospital because of an asymptomatic cystic nodule on the right side of the neck. A computed tomography and a fine needle biopsy of thyroid tumor revealed that the tumor might be metastatic lymph node from papillary thyroid carcinoma. Total thyroidectomy and lymph node dissection were performed. Histologic examination of the resected specimen from the tumor of the right neck revealed moderately differentiated squamous cell carcinoma. This cystic tumor had rich lymphatic follicle like a branchial cleft. The inner wall of this tumor was lined with squamous epithelium and demonstrated that it is gradual transition from benign to malignant. Although a possibility of metastatic tumor was considered, no primary site was discovered on subsequent examinations. This case satisfied three out of the Martin's four criteria for diagnosis of branchiogenic carcinoma. Therefore, this case was diagnosed as double cancer of papillary thyroid carcinoma and branchiogenic carcinoma. In the diagnosis of a thyroid tumor with a cystic lesion of the neck, not only metastatic lymph node from thyroid tumor but branchiogenic carcinoma or other disease should be taken into consideration, even if the primary thyroid tumor was diagnosed as papillary carcinoma before operation.
