LAUSR

Intrathyroid thyroglossal duct cysts are rarely reported when unassociated with clinical complaints [1–3]. To our knowledge, seven cases have been reported in adults since 1998. The ages of the patients ranged from 41 to 78 years, with women being more frequently affected (4 versus 3). The cyst sizes ranged from 0.7 to 4.4 cm [4–8]. We had the opportunity to observe two such intrathyroid cysts accompanied by ectopic thymus (intrathyroid and cervical) that were incidentally detected on thyroidectomy specimens. The first cyst was found in a patient with Graves’ disease who presented with hyperthyroidia and experienced a miscarriage during the medical treatment [9]. Thyroidectomy was performed. Microscopically, the background thyroid showed lymphocytic thyroiditis and adenoma-type nodules. In addition, several ectopic tissue foci, including skeletal muscle, thymic tissue, parathyroid tissue, and adipose tissue, were found dispersed in the thyroid (Fig. 1). A 5-mm intrathyroidal cyst surrounded by hyperplastic thyroid follicles resulting in a partially encapsulated adenoma-type nodule was identified. The hyperplastic thyroid follicles were heterogeneous in size. These follicles were positive for TTF1, and—surprisingly—were also positive for HBME1 and focally positive for cytokeratin CK19 and syndecan-1/ CD138. However, there were no nuclear features of papillary thyroid carcinoma. The cyst was lined by squamous or nondescript cells (with rare interspersed ciliated cells) that were positive for CK19, CK5/6, p63 and, syndecan-1 on immunohistochemistry. A rim of fibrous tissue surrounded the squamous epithelium. There were no pathological changes in the parathyroid glands, either on scintigraphy or perioperatively. A second cyst was identified in a patient who underwent thyroidectomy for multinodular goiter (a 3-cm large nodule with hyperfixing on scintigraphy) during surgery for hyperparathyroidemia. The thyroid contained a 4-mm cyst lined by a pluristratified epithelium composed of flat, mainly spindle-shaped cells (Fig. 2). Rare ciliated cells were also seen. P63, CK5/6, Bcl-2, HBME1, and syndecan-1 were expressed by basal and some suprabasal cells. TTF1 was expressed in basal cells; the upper cells were negative or faintly stained. The cyst was surrounded by fibrous tissue. The left P4-neck dissection specimen contained one parathyroid gland that showed multifocal nodular hyperplasia (alternating with adipose involution) on microscopy. The left P3-neck dissection specimen, which extended from the P3 zone (where no parathyroid was detected) downwards, contained a thymus-parathyroid unit (TPU). Both parathyroid and thymic tissues showed adipose involution. The right parathyroid glands, which were perioperatively identified in the perithyroid area, were enlarged. We herein reported two cases of intrathyroid infracentimetric cysts with a squamous cell lining that were incidentally identified on thyroidectomy specimens. The presence of a squamous cell-lined cyst with focal ciliated cells and distinct surrounding thyroid tissue indicated a thyroglossal duct remnant rather than squamous cell metaplasia in cystic adenoma. The presence of dispersed parathyroid, thymic and, skeletal muscle tissues along with a thyroglossal cystic duct in the thyroid of the 1st case and of a * Adriana Handra-Luca [email protected]; [email protected]