Thyroglossal duct (TGD) carcinoma is a rare malignant tumor arising from remnants of thyroid tissue or the wall of the duct and generally occurs along the anatomic course of the TGD. TGD carcinoma originating in the hyoid bone is extremely rare but can occur since the TGD penetrates the hyoid bone on rare occasions. This report describes the case of a 30-year-old man with TGD carcinoma originating in the hyoid bone. Computed tomography demonstrated a mass in the hyoid bone that expanded the cortical bone of the hyoid. The mass had a central solid component with calcification and a marginal cystic component. When we encounter a calcified mass in the hyoid bone, we should consider TGD carcinoma among the differential diagnoses.
Thyroglossal duct (TGD) carcinoma is a rare malignant tumor arising from remnants of thyroid tissue or the wall of the TGD. This neoplasm may occur within a thyroglossal duct cyst on some occasions. TGD carcinoma generally occurs along the anatomic course of the TGD, which begins at the foramen cecum, loops around the hyoid bone, and descends anteriorly to the thyrohyoid membrane, uncommonly penetrating the hyoid bone [
A 30-year-old man presented to our hospital complaining of a six-month history of progressive neck swelling and sore throat. He had no pertinent past medical history. Physical examination revealed a 4-cm, hard mass in the right anterior neck. Results of thyroid functional tests, such as serum thyroxine (T4), free triiodothyronine (T3), and thyroid stimulating hormone (TSH), were within normal limits. Other laboratory findings were also unremarkable.
Computed tomography (CT) demonstrated a heterogeneous mass at the level of the hyoid bone, 35 × 47 × 38 mm in size, expanding the cortical bone of the hyoid (Figure
CT of the neck. (a) Axial noncontrast CT at the level of the hyoid bone shows a well-defined, low-density mass expanding the cortex of the hyoid bone with partial bone destruction (arrow). Punctate calcifications are seen within the mass (arrowhead). (b) Axial contrast-enhanced CT at the same level as (a) shows marked enhancement of the solid component (arrow). (c, d) Sagittal at the midline (c) and axial at the infrahyoid level (d) images of contrast-enhanced CT show the mass consists of a solid component and a marginal cystic component (arrows). Left submental lymphadenopathy is also seen (arrowhead).
MRI of the neck. (a) T2-weighted image at the level of the hyoid bone shows intermediate signal intensity corresponding to the solid component (arrow) and high signal intensity corresponding to the cystic component (arrowhead). (b) Contrast-enhanced fat-suppressed T1-weighted image at the same level as (a) shows marked enhancement of the solid component (arrow). Left submental lymphadenopathy is also seen (arrowhead).
Fine needle aspiration of the mass showed papillary carcinoma. Given the imaging findings of expanded cortical bone in the hyoid and FNA findings, we suspected primary papillary carcinoma originating from ectopic thyroid gland tissue associated with a thyroglossal duct remnant in the hyoid bone.
The patient underwent tumor resection and left neck dissection of level I-III. Right neck dissection was not performed, because only left submental lymph node metastasis was suspected from imaging. We usually do not perform preventive neck dissection for thyroid papillary carcinoma in our hospital. The resected specimen showed an ill-defined, whitish mass with calcification measuring approximately 3 cm along the longest axis. Histopathological examination showed papillary adenocarcinoma with calcification (Figure
Histopathological finding of the hyoid bone tumor. (a) Microscopically, the tumor comprises atypical cell forming papillae, corresponding to thyroid papillary carcinoma. (b) Thyroid follicles are also seen around the malignant component [hematoxylin-eosin staining; magnification: 400× (a), 100× (b)].
Additional thyroid suppression therapy was administered after surgery. The addition of total thyroidectomy and radioactive iodine ablation was not performed to preserve thyroid function because the surgical margins were negative and cancer in the thyroid gland was not suspected from imaging. The patient has been followed up for six months without local recurrence or metastasis.
Carcinomas arising from the anatomical course of the TGD are quite rare. The mean age at presentation of TGD carcinoma is about 40 years. TGD carcinoma tends to be more common in the female population (68.3%). The most common pathology of TGD carcinoma is papillary carcinoma (92.1%) arising from ectopic thyroid tissue, followed by squamous carcinoma (4.3%), which is hypothesized to originate from the wall of the TGD [
Imaging findings of TGD carcinoma remain lacking in the literature. It is important to differentiate TGD carcinoma from thyroglossal duct cyst or other benign pathologies. On ultrasound, a mural mass with associated microcalcifications is suggestive of TGD carcinoma [
In the present case, the neck mass was thought to originate in the hyoid bone because the tumor expanded the cortical bone of the hyoid. Differential diagnoses of tumors originating in the hyoid bone vary from benign to malignant lesions. Benign conditions include osteoma, chondroma, aneurysmal bone cyst, and giant cell tumor, and malignant conditions include chondrosarcoma, osteosarcoma, solitary plasmacytoma, and metastatic bone tumors. Most pathologies can be differentiated easily from imaging findings, but excluding the possibility of chondrosarcoma or metastasis by imaging alone is difficult.
TGD is formed along the pathway of normal caudal migration of the thyroid gland. The thyroid gland originates as an invagination of proliferating endodermal cells in the floor of pharynx, which later becomes the foramen cecum in the 3rd to 5th weeks of gestation. The thyroid primordium descends caudally and reaches the paratracheal position in the 7th week of gestation, and then the TGD involutes and atrophies between the 8th and 10th weeks of gestation. The normal anatomic course of the TGD begins at the foramen cecum, then loops around the hyoid bone anteriorly, inferiorly, and posteriorly, and descends anteriorly to the thyrohyoid membrane to reach the normal position anterior to the trachea [
The standard treatment for TGD carcinoma is a Sistrunk procedure. The addition of neck dissection and total thyroidectomy remains controversial. Neck dissection is necessary when cervical lymph node metastasis is recognized, but preventive neck dissection is not always necessary [
We encountered an extremely rare case of TGD carcinoma originating in the hyoid bone. The TGD uncommonly courses within the hyoid bone but may penetrate the hyoid bone on rare occasions. When we encounter a calcified mass in the hyoid bone, we should consider the possibility of TGD carcinoma as one of the differential diagnoses.
The authors declare that there are no conflicts of interest regarding the publication of this paper. None of the authors have any direct or indirect conflicts of interest, financial or otherwise, related to the subject matter contained in this report.