2024 Volume 117 Issue 6 Pages 565-572
Introduction: There are two types of thyroid cysts: true cysts and secondary cysts; true cysts are rare, and the majority are secondary cysts. In this report, we describe two cases of true epithelial cysts of the thyroid gland.
Case 1: A 70-year-old man was referred to us with an abnormal mediastinal shadow on the chest X-ray detected during a physical checkup. Chest CT revealed a cystic lesion measuring 6 cm in diameter, extending from the lower pole of the right lobe of the thyroid gland to the mediastinum. The lesion was excised through a combined approach of external cervical incision and thoracoscopic surgery. It was found to be strongly adherent to the right recurrent laryngeal nerve, which could not be dissected thoracoscopically. The recurrent laryngeal nerve was transected under the collarbone. The histopathological diagnosis was an epithelial cyst.
Case 2: A 71-year-old man presented with the complaint of a cervical mass. Ultrasonography revealed a cystic lesion measuring 4 cm in diameter in the right lobe and a hypoechoic nodule measuring 7 mm in the left lobe of the thyroid gland. Total thyroidectomy was performed. The histopathological diagnosis of the lesion in the right lobe was epithelial cyst, while that of the nodule in the left lobe was papillary thyroid carcinoma.
Discussion: The two cases were considered as possible cases of thyroglossal duct cysts. Epithelial cysts are rarely found in the thyroid gland, and it is difficult to distinguish them from secondary cysts prior to surgery. Epithelial cysts may have fibrous connective tissue or lymphoid tissue under the epithelium.
Conclusion: We encountered two cases of epithelial cysts in the thyroid gland. Epithelial cysts may adhere to the surrounding tissues, and care must be taken not to damage surrounding tissues, such as nerves, during surgery.
