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thyroglossal duct remnants represent a common developmental abnormality of the thyroid gland , and thyroglossal duct carcinoma ( tgdc ) reportedly occurs in approximately 1% of all thyroglossal duct remnants .
the incidence of lymph node metastases in papillary carcinoma of tgdc is rare ( 7% to 15% ) , compared with the incidence in primary papillary thyroid carcinoma .
carotid body tumors ( cbts ) are rare , benign neoplasms that originate from the neuroectodermal paraganglion .
originating from the afferent ganglion of the glossopharyngeal nerve , carotid body tumors are generally located at the carotid bifurcation .
physiological activity is rare in these neoplasms , and these tumors generally exhibit a slow rate of growth , most often presenting asymptomatically as a space - occupying mass lesion noted clinically or radiographically . to our knowledge , tgdc with neck metastasis accompanied by a cbt has not been reported previously .
in addition , the cbt in the present case mimicked neck metastasis from the tgdc .
we present a case of the cbt mimicking neck metastasis from the tgdc with a review of literature .
a 78-year - old woman visited our clinic , presenting with a 3-year history of a midline neck mass in the region of the hyoid bone and bilateral cervical asymptomatic neck masses .
there were no constitutional symptoms , including fever , night sweating , fatigue , dysphagia , dyspnea , and weight loss .
physical examination showed a 33-cm rubbery , non - tender , semi - fixed midline mass and several enlarged lymph nodes at level ii and iii bilaterally .
the results of routine laboratory tests , including blood chemistry , complete blood cell count , coagulation study , serologic testing , and urine analysis , were unremarkable . electrocardiogram and chest x - ray were within normal limits .
computed tomography ( ct ) with contrast showed an irregularly marginated , round , heterogeneously enhancing mass at the level of the hyoid bone and multiple enlarged lymph nodes bilaterally at level ii to iii ( fig .
interestingly , the left - side neck mass was located at the carotid bifurcation , splaying the carotid bifurcation on a ct scan ( fig .
however , the ct scan did not indicate other instances of abnormal lymphadenopathy in the left neck .
furthermore , neck ct and sonography did not demonstrate any mass involving the thyroid ( fig .
fine needle aspiration biopsy ( fnab ) was done on the midline mass and right - side neck mass .
the results of fnab suggested the possibility of papillary carcinoma and lymph node metastasis from papillary carcinoma , respectively . from the above results
we planned to resect the masses , including bilateral neck dissection , in accordance with tgdc with neck metastasis .
splaying of the carotid bifurcation , however , is usually indicative of a cbt . through the head and neck tumor board
, we decided that carotid arteriography should be preoperatively performed to differentiate a cbt from lymph node metastasis .
the mass was confirmed as a highly vascular mass in the bifurcation of the carotid artery that was compressing the internal and external carotid arteries ( fig .
our patient did not undergo carotid occlusion testing and embolization because of the potential complications .
subsequently , the patient underwent wide excision of the midline neck mass , including resection of the hyoid bone , total thyroidectomy , central neck dissection and right - side selective neck dissection ( levels ii - v ) , involving resection of the sternocleidomastoid muscle , spinal accessory nerve , and internal jugular vein .
although there was mild adhesion between the midline mass and surrounding soft tissue , we obtained a generous resection margin ( fig .
, we confirmed the cbt between external and internal carotid artery ( fig . 2c ) .
we did not try to remove the left - side neck mass ( cbt ) because it had a tendency to bleed when touched and the patient was elderly .
histological analysis revealed that a thyroglossal duct cyst was lined by a single row of columnar epithelium and the tumor was composed of small and large papillary structures with fibrovascular cores ( fig .
in addition , the tumor cells lining the papillary structures of the midline mass and cervical lymph nodes showed nuclear grooves and nuclear clearing , which are characteristic nuclear features of papillary carcinoma ( fig .
the final histopathologic diagnosis was consistent with tgdc papillary carcinoma with perithyroidal soft tissue extension and subsequent multiple lymph node metastasis ( 17 out of 55 lymph nodes ) .
however , we could not demonstrate any evidence of papillary carcinoma in the thyroid gland .
the patient refused adjuvant therapy with i after surgery and was only treated with levothyroxine supplementation . at the 2-year follow - up ,
although a thyroglossal duct remnant is the most common congenital midline neck mass , tgdc is thought to be extremely rare , occurring in approximately 1% of all diagnosed thyroglossal duct remnants .
the most common presentation is the development of an asymptomatic lateral neck mass without a thrill or bruit .
cranial nerve deficits are uncommon but may be seen in patients with masses greater than 5 cm in diameter [ 4 , 5 ] . in the present case , the patient had no specific symptom except multiple neck masses . on the rare occasion when tgdc is suspected clinically , preoperative physical examination , sonography , ct , mri , and fna may be helpful . on physical examination , a neck mass that moves with swallowing and tongue movement
the most common ct findings of tgdc are a solid nodule in the cyst , followed by calcification , an irregular margin , and a thick wall . these findings , except calcification , corresponded to those in the present case .
furthermore , the ct scan in the present case demonstrated multiple conglomerated lymphadenopathies , suggestive of malignancy , and fnab of the midline and right - side neck masses indicated the possibility of papillary carcinoma . in cbt
, either contrast - enhanced ct or mri will clearly demonstrate a paraganglioma expanding the carotid bifurcation .
the diagnosis of cbt is generally confirmed by carotid arteriography that shows a highly vascular tumor enlarging the space between the internal and external carotid arteries .
however , it was easier to overlook the possibility of a cbt in the present case for the preoccupation of neck metastasis from tgdc .
considering the splaying of the carotid bifurcation revealed by the ct scan , we fortunately suspected the possibility of left - side cbt .
.   described three definitive criteria for distinguishing between primary tgdc and metastatic disease from a primary lesion inside the thyroid gland .
second , the tgdc must be differentiated from a cystic lymph node metastasis by histological demonstration of a squamous or columnar epithelial lining and normal thyroid follicles in the wall of the thyroglossal duct cyst .
third , malignancy should not be present in the thyroid gland or any other possible primary site .
the nonfamilial association of carotid body tumors and papillary carcinomas of the thyroid was first described in 1968 .
it is unclear that whether there is a common pathogenesis for carotid body tumors and differentiated thyroid carcinomas , but larraza - hernandez et al .   and kuratomi et al .  
reported differentiated thyroid carcinomas associated with carotid body tumors . because tgdc accompanied by a cbt has not been reported previously , it is necessary to search for tgdc as well as carotid body tumors in order to learn more about this association .
the most frequently used surgical therapeutic approach for tgdc is the sistrunk procedure , which includes en - bloc resection of the thyroglossal duct cyst along with the tract , the middle part of the hyoid bone , and the soft tissues along the course of the thyroglossal duct to the level of the foramen cecum .
the incidence of cervical lymph node metastasis from tgdc has been reported to be 7 to 15% . when cervical lymph node metastasis is present , a reasonable approach is to perform a sistrunk procedure , a total thyroidectomy , and selective neck dissection at an appropriate level .
accordingly , for asymptomatic elderly patients , the indolent nature of cbts has led to the recommendation of surveillance . in our case ,
the patient underwent wide excision of the midline neck mass , including resection of the hyoid bone , total thyroidectomy , central neck dissection and selective neck dissection ( levels ii - v ) .
however , we left the cbt unresected because we surmised that this cbt would not influence the life expectancy of this patient . in tgdc
, additional therapy is indicated if there is involvement of the thyroid gland , soft tissue invasion , or lymph node metastases .
ablation - dose radioactive iodine should follow , with subsequent scanning to exclude further tumor foci , as is standard practice for the majority of well - differentiated thyroid carcinomas .
few reports about tgdc or cbt are present in the literature , and this is the first reported case involving the coexistence of tgdc with neck metastasis and cbt .
if we had missed the possibility of cbt in the left - side neck mass , we would likely have encountered unexpected bleeding from the tumor and adhesion between the tumor and carotid artery during the left - side neck dissection .
the present case demonstrates the importance of performing a careful physical examination and thorough evaluation of preoperative imaging studies before initiating surgical treatment of various head and neck tumors .
thyroglossal duct carcinoma is uncommon , occurring in approximately 1% of all thyroglossal duct remnants . 
 this rare neoplasm is characterized by relatively nonaggressive behavior with infrequent lymph nodal spread . 
 another rare neoplasm of the head and neck region is a carotid body tumor . 
 a 78-year - old woman with a 3-year history of midline and bilateral neck masses was referred to us . 
 fine needle aspiration biopsies and a computed tomography scan suggested the diagnosis of thyroglossal duct carcinoma with cervical lymph node metastasis . 
 interestingly , the left - side neck mass was found to be splaying the carotid bifurcation , on computed tomography imaging . 
 carotid arteriography demonstrated a highly vascular mass in the bifurcation of the carotid artery that was compressing the internal and external carotid arteries . to our knowledge , this is the first reported instance of a thyroglossal duct carcinoma with neck metastasis accompanied by a carotid body tumor . 
 in addition , the carotid body tumor in this case mimicked neck metastasis from the thyroglossal duct carcinoma .