as a common head and neck cancer , nasopharyngeal carcinomas are generally either keratinizing or nonkeratinizing squamous cell carcinomas . primary nasopharyngeal adenocarcinomas ( npacs ) are rare neoplasms , constituting only 0.38% to 0.48% of all malignant nasopharyngeal neoplasms . thyroid - like low - grade nasopharyngeal papillary adenocarcinoma ( tl - lgnppa ) is a small minority of conventional nasopharyngeal adenocarcinoma that exhibits papillary growth and abnormal expression of thyroid transcription factor 1 ( ttf-1 ) . to the best of our knowledge , only thirteen cases have been reported in the english - language literature and eleven in the chinese - language literature to date ( table 1 ) . in this article , we present a case of primary tl - lgnppa and an analysis of its clinicopathological features . a 15-year - old chinese girl presented with a complaint of rhinorrhoea and nasal congestion with a duration of 1 month . on clinical examination , no thyroid tumor or other physical abnormalities were found . nasal endoscopy identified a pedunculated polypoid mass with smooth surface that measured approximately 2.52 cm arising from the posterior nasal septum ( fig . follow - up data showed no signs of local recurrence at up to 2 years after complete surgical removal . the tissue was fixed in formalin and embedded in paraffin , after which 4-m thin sections were cut and stained with hematoxylin and eosin . immunohistochemical staining was performed using commercially available antibodies to the following antigens : pan - cytokeratin ( ckpan ) , epithelial membrane antigen ( ema ) , vimentin , cytokeratin ( ck ) 7 , cd15 , thyroid transcription factor 1 ( ttf-1 ) , ki-67 , p40 , s100 , glial fibrillary acidic protein ( gfap ) , ck20 , cdx-2 , and thyroglobulin . at the same time , in situ hybridization for the presence of small epstein - barr virus ( ebv)encoded rna was performed to identify the association between this tumor and ebv . histological examination of the biopsy specimen revealed a tumor that showed papillary configuration with hyalinized fibrovascular cores , similar to thyroid papillary carcinoma ( fig . the papillae were complex and tightly packed , and most were lined with cuboidal or columnar epithelia containing overlapping round to ovoid nuclei that displayed fine chromatin and mildly eosinophilic cytoplasm ( fig . 2c ) . small intra - nuclear cytoplasmic inclusions were present focally , although neither nuclear grooving nor ground glass nuclei were found . in small parts of the tumor , no necrosis or mitotic activity was discerned and no continuity between the tumor epithelia and normal nasopharyngeal mucosa or mucous glands was identified . immunoperoxidase studies showed that neoplastic cells were positive for ck7 , vimentin , ttf-1 , ckpan , and ema ( fig . there was no immunoreactivity for thyroglobulin , cd15 , s100 , p40 , ck20 , cdx-2 , and gfap . in the most concentrated spot , npac contains two subtypes : conventional / surface origin - type and salivary gland - type . the latter includes polymorphous low - grade adenocarcinoma , mucoepidermoid adenocarcinoma , and adenoid cystic carcinoma . in 1988 , wenig et al . first described thyroid - like papillary adenocarcinoma of the nasopharynx and proposed that these papillary adenocarcinomas should been regarded as a distinct entity from conventional adenocarcinomas in this region based on their indolent clinical behavior and low - grade histological features . nasopharyngeal papillary adenocarcinoma ( nppa ) was enrolled in the world health organization classification system of malignant epithelial tumors of the nasopharynx in 2005 . papillary configuration and aberrant ttf-1 expression are the distinguishing features of tl - lgnppa , mimicking papillary thyroid carcinoma ( ptc ) . tl - lgnppa is an extremely rare neoplasm . to the best of our knowledge , the median age is 35 years in patients , ranging from 9 to 68 years . instances of tl - lgnppa were usually localized in the roof of the nasopharynx and posterior edge of the nasal septum . the excellent prognosis was obvious , with local excision being performed in all reported cases , and no local recurrence or metastasis reported . histologically , these neoplasms frequently exhibit papillary architecture lined by moderately pleomorphic columnar epithelial cells with fibrovascular cores , overlapping nuclei with clear optically chromatin , and psammoma bodies . however , the biphasic pattern of low - grade nppa with a spindle cell component has been described in three case reports . in this case , no obvious spindle cell component was observed . the biphasic pattern of tl - lgnppa should be further investigated if a large number of cases can be collected . immunohistochemically , the positive expression of ttf-1 was the most characteristic feature of tl - lgnppa . as a homeodomain containing transcription factor coded by nkx2 - 1 , ttf-1 is usually found in lung , thyroid , and central nervous system tissue . nevertheless , the positive expression of ttf-1 was also observed in other organs , including endometrium , colon , and breast . although the etiology of ttf-1 positive staining in tl - lgnppa is still not clear , three mechanisms to explain this phenomenon were proposed in a recent case report . second , a gene rearrangement that affects ttf-1/nkx2 - 1 may result in abnormal expression of ttf-1 . finally , genetic instability and reprogramming of the cancer cells can cause dis - differentiation and lead to deregulation of ttf-1/nkx2 - 1 . however , these presumptions are poorly evidenced owing to the extreme rarity of this tumor at the present time . there are limited options available for differential diagnosis of papillary lesions in the nasopharynx . because tl - lgnppa display a striking resemblance to ptc , it is important to exclude nasopharyngeal metastasis from papillary adenocarcinoma of the thyroid gland for accurate diagnosis , treatment , and prognosis of the patient . immunostaining for thyroglobulin and cd15 are critical and highly recommended to distinguish these two entities . however , a case of tl - lgnppa with focal expression of thyroglobulin was recently reported . polymorphous low - grade papillary adenocarcinoma ( plga ) is more aggressive and positive for vimentin and s100-protein . to date , positivity for ttf-1 has never been reported in plga . papillary variants of the intestinal type of adenocarcinoma ( itac ) show more nuclear atypia and commonly display mucinous differentiation . acinic cell carcinomas ( acc ) with a papillary component are frequently cystic and variably positive for s100-protein and vimentin according to the range of differentiation ( acinar to intercalated ducts ) . extraventricular choroid plexus papillomas ( cpp ) at unusual localization must be taken into consideration , most of them was positive for s100 and negative for ema , part of them was positive for gfap . in our report , negative staining for thyroglobulin , cd15 , s100 , gfap , ck20 , and cdx-2 was revealed ; therefore , ptc , plga , itac , acc , and cpp should not be considered for accurate diagnosis . it has been well documented that tumors originating from the nasopharyngeal epithelium were associated with the ebv . investigation of in situ hybridization for ebv revealed negative results , which is concordant with reports by wu et al . a close relationship between tl - lgnppa and ebv was not confirmed ; however , further investigation is needed because of the rarity of this neoplasm . to date , no case of lymphatic metastasis or recurrence has been reported , indicating excellent prognosis for patients with thyroid - like papillary adenocarcinoma . generally , surgical excision is adequate for the treatment of tl - lgnppa . when surgical excision is not feasible or positive surgical margins have been observed , radiotherapy can be employed as an adjuvant treatment . in conclusion , we present here a novel case of tl - lgnppa with a review of its main clinicopathological features . due to the rarity of this neoplasm and favorable clinical outcome , clinicians should pay more attention to accurate diagnosis of this entity , as well as its treatment and clinical prognosis .