embryologically , failure of the thyroid gland to separate from the base of the tongue results in a lingual thyroid , which accounts for 90% of ectopic thyroids . remnant thyroid tissue can be demonstrated at the base of the tongue in up to 10% of autopsy specimens ( 1 ) . most cases are asymptomatic but symptomatic patients have dysphagia ( 50% ) , dysphonia ( 44% ) , or dyspnea ( 28% ) . lingual thyroid has an absolutely characteristic ct appearance : its iodine content causes it to have very high attenuation values in relation to surrounding soft tissue . the mass of ectopic thyroid tissue usually lies in the center of the tongue base within intrinsic muscle ; intravenous contrast enhancement will increase the differential density between thyroid tissue and surrounding musculature ( fig . 1 ) . rarely , a lingual thyroid has been found to show inhomogeneous contrast enhancement on ct , resulting from marked thyroiditis and goitrous changes ( 2 ) . if the thyroid gland can not be found in its usual location , radionuclide scanning is necessary to determine the size , location and activity of thyroid tissue . because the radiation dose required is lower , the use of technetium-99 m pertechnetate is preferred to iodine 131 . thyroglossal duct cyst ( tgdc ) commonly presents as a midline anterior neck cyst at any point along the path from the foramen cecum of the tongue to the pyramidal lobe of the thyroid gland . it results from the persistence and dilatation of remnants of an epithelial tract formed during migration of the thyroid during the period of embryogenesis ( 3 ) . in 85% of cases lingual tgdc is a rare form , and only 2% of tgdcs are located at the base of the tongue ( 3 ) . a tgdc usually contains thick , gelatinous mucoid fluid , and microscopically , may be lined with transitional , cuboidal , columnar or stratified squamous epithelium , and this may be ciliated or non - ciliated . depending on its oral pharyngeal location , lingual tgdc may cause dysphagia or dyspnea . ct characteristically reveals a lingual tgdc as a well - circumscribed , homogeneous low - density lesion , the values of which correspond to those of fluid ( 10 - 18 hu ) ( fig . depending on this content , t1-weighted imaging of an uncomplicated tgdc demonstrates low to intermediate signal intensity , while t2-weighted images are hyperintense . unless inflammation is present , the cyst wall is usually thin and non - enhancing ( 4 ) . bronchogenic cyst is the most common type of intrathoracic foregut cyst , and results from anomalous budding or branching of the tracheobronchial tree during development ( 5 ) . for this cyst to be classified as bronchogenic in origin , it must be lined by columnar respiratory epithelium and contain seromucous glands . microscopically , it is lined by ciliated pseudostratified epithelium of the respiratory type , but in parts there may be patches of squamous metaplasia ( fig . 3 ) . the cyst wall frequently contains bundles of smooth muscle , mucous and mixed glands , as well as cartilaginous nodules and plates . ct usually demonstrates a cystic mass molding the surrounding structures , and the cyst may be uni- or multilocular ( 5 ) . unless complicated by infection or hemorrhage , the size of a bronchogenic cyst is usually stable , and the density of its contents is near that of water , ranging from -10 to + 10 hu ( fig . the essential difference between dermoid and epidermoid cyst lies in the presence of skin appendages within the wall of the former and the absence of these features in the latter ( 6 ) . because of its squamous epithelial lining when an epidermoid cyst occurs in the oral cavity , the floor of the mouth is most commonly involved , though sites which include the lips , tongue , and buccal mucosa have also been reported . epidermoid cyst is typically revealed by ct as a well - defined , lobulated mass with hypoattenuation similar to that of fluid . peripheral enhancement may be revealed by contrast - enhanced ct , but central enhancement within the tumor is unusual . mr imaging of an epidermoid cyst typically depicts a cystic mass , hypointense on t1-weighted images and hyperintense on t2-weighted images ( fig . the use of contrast material shows that the cyst wall is 2 - 6 mm thick ( fig . venous malformations ( vms ) are part of a spectrum of benign vascular lesions commonly found in the pediatric population , and may occasionally be difficult to distinguish solely on the basis of their clinical appearance . on the basis of their histologic features , mulliken and glowacki classified congenital vascular anomalies as true hemangiomas or one of a variety of vascular malformations ( 7 ) . the latter are true congenital lesions , which by definition are always present at birth , though are not always detected ( 8) . they are classified according to the main channel type present : capillary , lymphatic , arterial , venous , or mixed ( 7 ) . vascular lesions have been further categorized on the basis of their hemodynamic characteristics as low- or high - flow types , a distinction that is important when choosing the management strategy . whereas true hemangiomas often involute with age , vascular malformations remain stable or slowly grow with the patient and typically require some form of therapy when cosmetic disfigurement , bleeding , or functional impairment occurs . conventional radiographs , though generally of little use , are invaluable if they demonstrate the presence of phleboliths , as these are pathognomonic of vm . ct and mri provide good anatomic detail , with precise delineation of the extent of lesions and their relation to surrounding structures ( fig . in addition , mr imaging is helpful in that when flow void is identified , it can further characterize the type of flow present . angiography can be invaluable for delineating feeding and draining vessels and in defining the hemodynamics of vascular lesions . since its findings are generally normal , it does not , however , contribute to the diagnosis of vm ( 9 ) . the characteristic features of vm are noted after direct intralesional puncture and lesion opacification , with the demonstration of tortuous , dilated venous channels and the absence of arteriovenous communication . thus , angiography can help rule out high - flow vascular malformation , with its arterial components .
because the tongue is superficially located and the intial manifestation of most diseases occurring there is mucosal change , lingual these lesions can be easily accessed and diagnosed without imaging analysis . 
 most congenital lesions of the tongue , however , can manifest as a submucosal bulge and be located in a deep portion of that organ such as its base ; their true characteristics and extent may be recognized only on cross - sectional images such as those obtained by ct or mri . 
 in addition , because it is usually difficult to differentiate congenital lesions from other submucosal neoplasms on the basis of imaging findings alone , clinical history and physical examination should always be taken into consideration when interpretating ct and mr images of the tongue.although the radiologic findings for congenital lesions are nonspecific , ct and mr imaging can play an important role in the diagnostic work - up of these unusual lesions . 
 delineation of the extent of the tumor , and recognition and understanding of the spectrum of imaging and the pathologic features of these lesions , often help narrow the differential diagnosis .