document: adamantinoma of the tibia is a rare slow - growing primary tumor of the bone . 
   there has been much controversy on the origins of this tumor with one major focus being the relationship between osteofibrous / fibrous dysplasia and adamantinoma . 
   there have been approximately 300 cases of tibial adamantinoma reported in the published english language literature . of these cases , 1520% 
   the most common site of metastasis is to the lungs . as metastases to the regional lymph nodes 
   are rare , there is limited information regarding the best practice plan for their management in the literature . 
   we report 2 cases of tibial adamantinoma , which were problematic from a diagnostic point of view . 
   case 2 is of a tibial adamantinoma that presented with groin metastases which was initially diagnosed as a cutaneous adnexal carcinoma . 
   a review of inguinal nodal metastatic adamantinoma is outlined in addition to the clinic - pathological data on these cases . 
   in 2007 , a 29-year - old female presented with a swelling in her left inguinal area . 
   investigations including a computed tomography ( ct ) scan showed an extremely large heterogeneous , hyperdense , lobular lymph node centered in the left inguinal region measuring 6.54.6 cm . 
   histopathological examination revealed the presence of a malignant neoplasm that was composed of sheets of basaloid cells with round vesicular nuclei and minimal cytoplasm . 
   this lesion was interpreted as a cutaneous eccrine carcinoma ( figure 1a  c ) . due to the unusual diagnosis , 
   an external consultation and a request for additional clinical history were obtained . on detailed review , 
   the pathological report was reinterpreted as metastatic adamantinoma in conjunction with a confirmed past clinical history of surgical excision of a left tibial adamantinoma three years previously in 2004 . 
   the specimen consisted of a firm rubbery mass of fibro - fatty tissue that measured 18.511.37.2 cm with an ellipse of skin measuring 820.3 cm . 
   the cut surface revealed a multi - lobulated light brown well - circumscribed mass that measured 10.475.5 cm . on microscopic examination , 
   the neoplastic cells were composed of predominantly basaloid and tubular nests of malignant cells with some peripheral palisading ( figure 1d  f ) . 
   the histomorphological appearance of these cells was identical to the previous histology in this case ( figure 1a  c ) confirming the presence of inguinal lymph nodal metastases from adamantinoma of the tibia . 
   biopsy of left inguinal mass ( a , b , c ) and left inguinal lymphadenopathy ( d , e , f ) . 
   photomicrographs of hematoxylin and eosin stained slides at low power ( lens objective 2 ) shows the presence of a malignant neoplasm in the subcutaneous fat ( a ) . 
   lesional cells are composed predominantly of basaloid cells with round vesicular nuclei and minimal cytoplasm as seen at medium power ( b ) ( lens objective 4 ) and at high power ( c ) ( lens objective 10 ) . 
   photomicrographs of hematoxylin and eosin stained slides at low power ( lens objective 2 ) shows the presence of a metastatic malignant neoplasm in the lymph node (  ) ( d ) . 
   the neoplastics cells were composed of basaloid and tubular nests of malignant cells with some peripheral palisading as seen at medium power ( e ) ( lens objective 4 ) and at high power ( f ) ( lens objective 10 ) . 
   biopsy of left inguinal mass ( a , b , c ) and left inguinal lymphadenopathy ( d , e , f ) . 
   photomicrographs of hematoxylin and eosin stained slides at low power ( lens objective 2 ) shows the presence of a malignant neoplasm in the subcutaneous fat ( a ) . 
   lesional cells are composed predominantly of basaloid cells with round vesicular nuclei and minimal cytoplasm as seen at medium power ( b ) ( lens objective 4 ) and at high power ( c ) ( lens objective 10 ) . 
   photomicrographs of hematoxylin and eosin stained slides at low power ( lens objective 2 ) shows the presence of a metastatic malignant neoplasm in the lymph node (  ) ( d ) . 
   the neoplastics cells were composed of basaloid and tubular nests of malignant cells with some peripheral palisading as seen at medium power ( e ) ( lens objective 4 ) and at high power ( f ) ( lens objective 10 ) . in april 2009 , 
   a new node along the left external iliac in the retroperitoneum was detected and biopsied under radiological guidance . 
   histopathological examination showed similar findings confirming the presence of metastatic adamantinoma ( figure 2a and b ) . 
   ct scans of the chest showed the presence of two nodules in the right lung , which remained stable on follow up over the following year . 
   follow up in early 2011 shows stable residual disease with no additional findings of note . 
   photomicrographs of hematoxylin and eosin stained slide at low power ( a ) ( lens objective 2 ) shows the presence of a malignant neoplasm . 
   the neoplastic cells ( b ) at high power ( lens objective 10 ) shows a similar morphology of basaloid cells as seen in figure 1 . 
   photomicrographs of hematoxylin and eosin stained slide at low power ( a ) ( lens objective 2 ) shows the presence of a malignant neoplasm . 
   the neoplastic cells ( b ) at high power ( lens objective 10 ) shows a similar morphology of basaloid cells as seen in figure 1 . in 1999 , a 58-year - old female presented with a painful swelling on the mid shaft of her left tibia . 
   histopathological examination showed the presence of islands of woven bone in a background of bland spindled fibrous tissue , which was interpreted as fibrous dysplasia ( figure 3a and b ) . 
   nine years later , in 2008 , she was seen for a painful swelling in the same region , which had been increasing in size since her previous operation . 
   a wide excision of the lesion with a tibial allograft and intramedullary nail fixation was performed in october 2009 . 
   there was a predominant fibrous dysplasia like pattern consisting of cellular bland , spindled fibroblastic proliferation with scattered islands of woven bone . embedded within the spindle cells were occasional clusters of plump epitheliod appearing cells that had a corded arrangement in focal regions ( figure 3c ) . 
   immunohistochemistry confirmed the epithelial nature of these cells with strong positive staining to pankeratin antibodies ( figure 3d ) . 
   such areas were not identified even on retrospective detailed examination of the previous biopsy from 1999 . 
   photomicrographs of hematoxylin and eosin stained slides at low power ( lens objective 2 ) shows the presence of islands of woven bone amidst a background of bland fibrous spindle cells ( a ) . 
   medium power examination ( b ) ( lens objective 4 ) shows the presence of a rich fibro - collagenous stroma . 
   ( c and d ) 2009 histopathological examination of the tibial lesion photomicrographs of hematoxylin and eosin stained slides at low power ( lens objective 2 ) shows the presence of occasional clusters of plump epitheliod appearing cells with a corded arrangement in focal regions amidst a fibrous spindle background as seen ( c ) which are strongly positive to pankeratin antibodies on immunohistochemical examination ( d ) . 
   photomicrographs of hematoxylin and eosin stained slides at low power ( lens objective 2 ) shows the presence of islands of woven bone amidst a background of bland fibrous spindle cells ( a ) . 
   medium power examination ( b ) ( lens objective 4 ) shows the presence of a rich fibro - collagenous stroma . 
   ( c and d ) 2009 histopathological examination of the tibial lesion photomicrographs of hematoxylin and eosin stained slides at low power ( lens objective 2 ) shows the presence of occasional clusters of plump epitheliod appearing cells with a corded arrangement in focal regions amidst a fibrous spindle background as seen ( c ) which are strongly positive to pankeratin antibodies on immunohistochemical examination ( d ) . 
   the patient underwent revision surgery for non - union of the left tibia in 2010 . 
   in 2007 , a 29-year - old female presented with a swelling in her left inguinal area . 
   investigations including a computed tomography ( ct ) scan showed an extremely large heterogeneous , hyperdense , lobular lymph node centered in the left inguinal region measuring 6.54.6 cm . 
   histopathological examination revealed the presence of a malignant neoplasm that was composed of sheets of basaloid cells with round vesicular nuclei and minimal cytoplasm . 
   this lesion was interpreted as a cutaneous eccrine carcinoma ( figure 1a  c ) . due to the unusual diagnosis , 
   an external consultation and a request for additional clinical history were obtained . on detailed review , 
   the pathological report was reinterpreted as metastatic adamantinoma in conjunction with a confirmed past clinical history of surgical excision of a left tibial adamantinoma three years previously in 2004 . 
   the specimen consisted of a firm rubbery mass of fibro - fatty tissue that measured 18.511.37.2 cm with an ellipse of skin measuring 820.3 cm . 
   the cut surface revealed a multi - lobulated light brown well - circumscribed mass that measured 10.475.5 cm . on microscopic examination , 
   the neoplastic cells were composed of predominantly basaloid and tubular nests of malignant cells with some peripheral palisading ( figure 1d  f ) . 
   the histomorphological appearance of these cells was identical to the previous histology in this case ( figure 1a  c ) confirming the presence of inguinal lymph nodal metastases from adamantinoma of the tibia . 
   biopsy of left inguinal mass ( a , b , c ) and left inguinal lymphadenopathy ( d , e , f ) . 
   photomicrographs of hematoxylin and eosin stained slides at low power ( lens objective 2 ) shows the presence of a malignant neoplasm in the subcutaneous fat ( a ) . 
   lesional cells are composed predominantly of basaloid cells with round vesicular nuclei and minimal cytoplasm as seen at medium power ( b ) ( lens objective 4 ) and at high power ( c ) ( lens objective 10 ) . 
   photomicrographs of hematoxylin and eosin stained slides at low power ( lens objective 2 ) shows the presence of a metastatic malignant neoplasm in the lymph node (  ) ( d ) . 
   the neoplastics cells were composed of basaloid and tubular nests of malignant cells with some peripheral palisading as seen at medium power ( e ) ( lens objective 4 ) and at high power ( f ) ( lens objective 10 ) . 
   biopsy of left inguinal mass ( a , b , c ) and left inguinal lymphadenopathy ( d , e , f ) . 
   photomicrographs of hematoxylin and eosin stained slides at low power ( lens objective 2 ) shows the presence of a malignant neoplasm in the subcutaneous fat ( a ) . 
   lesional cells are composed predominantly of basaloid cells with round vesicular nuclei and minimal cytoplasm as seen at medium power ( b ) ( lens objective 4 ) and at high power ( c ) ( lens objective 10 ) . 
   photomicrographs of hematoxylin and eosin stained slides at low power ( lens objective 2 ) shows the presence of a metastatic malignant neoplasm in the lymph node (  ) ( d ) . 
   the neoplastics cells were composed of basaloid and tubular nests of malignant cells with some peripheral palisading as seen at medium power ( e ) ( lens objective 4 ) and at high power ( f ) ( lens objective 10 ) . in april 2009 , 
   a new node along the left external iliac in the retroperitoneum was detected and biopsied under radiological guidance . 
   histopathological examination showed similar findings confirming the presence of metastatic adamantinoma ( figure 2a and b ) . 
   ct scans of the chest showed the presence of two nodules in the right lung , which remained stable on follow up over the following year . 
   follow up in early 2011 shows stable residual disease with no additional findings of note . 
   photomicrographs of hematoxylin and eosin stained slide at low power ( a ) ( lens objective 2 ) shows the presence of a malignant neoplasm . 
   the neoplastic cells ( b ) at high power ( lens objective 10 ) shows a similar morphology of basaloid cells as seen in figure 1 . 
   photomicrographs of hematoxylin and eosin stained slide at low power ( a ) ( lens objective 2 ) shows the presence of a malignant neoplasm . 
   the neoplastic cells ( b ) at high power ( lens objective 10 ) shows a similar morphology of basaloid cells as seen in figure 1 . 
   in 1999 , a 58-year - old female presented with a painful swelling on the mid shaft of her left tibia . 
   histopathological examination showed the presence of islands of woven bone in a background of bland spindled fibrous tissue , which was interpreted as fibrous dysplasia ( figure 3a and b ) . 
   nine years later , in 2008 , she was seen for a painful swelling in the same region , which had been increasing in size since her previous operation . 
   a wide excision of the lesion with a tibial allograft and intramedullary nail fixation was performed in october 2009 . 
   there was a predominant fibrous dysplasia like pattern consisting of cellular bland , spindled fibroblastic proliferation with scattered islands of woven bone . embedded within the spindle cells were occasional clusters of plump epitheliod appearing cells that had a corded arrangement in focal regions ( figure 3c ) . 
   immunohistochemistry confirmed the epithelial nature of these cells with strong positive staining to pankeratin antibodies ( figure 3d ) . 
   such areas were not identified even on retrospective detailed examination of the previous biopsy from 1999 . 
   photomicrographs of hematoxylin and eosin stained slides at low power ( lens objective 2 ) shows the presence of islands of woven bone amidst a background of bland fibrous spindle cells ( a ) . 
   medium power examination ( b ) ( lens objective 4 ) shows the presence of a rich fibro - collagenous stroma . 
   ( c and d ) 2009 histopathological examination of the tibial lesion photomicrographs of hematoxylin and eosin stained slides at low power ( lens objective 2 ) shows the presence of occasional clusters of plump epitheliod appearing cells with a corded arrangement in focal regions amidst a fibrous spindle background as seen ( c ) which are strongly positive to pankeratin antibodies on immunohistochemical examination ( d ) . 
   photomicrographs of hematoxylin and eosin stained slides at low power ( lens objective 2 ) shows the presence of islands of woven bone amidst a background of bland fibrous spindle cells ( a ) . 
   medium power examination ( b ) ( lens objective 4 ) shows the presence of a rich fibro - collagenous stroma . 
   ( c and d ) 2009 histopathological examination of the tibial lesion photomicrographs of hematoxylin and eosin stained slides at low power ( lens objective 2 ) shows the presence of occasional clusters of plump epitheliod appearing cells with a corded arrangement in focal regions amidst a fibrous spindle background as seen ( c ) which are strongly positive to pankeratin antibodies on immunohistochemical examination ( d ) . 
   the patient underwent revision surgery for non - union of the left tibia in 2010 . 
   a literature search limited to the english language using the search terms adamantinoma of tibia and tibial adamantinoma and metastases and inguinal lymph node metastases was conducted . 
   research engines used included pubmed , medline , scopus , embase , and google / google scholar . 
   table 1 provides a comprehensive chronological review of 10 cases with inguinal lymph node metastases with details of reference number , year reported , author , sex , age at diagnosis , bone involved , location in bone , character and duration of symptoms + / history of trauma , latent period , treatment , and outcome . 
   , six cases with lymph node metastases as described in keeney 's study are not included in this table due to the lack of supporting clinical information . 
   similarly , cases with inguinal lymph node metastases as described in moon 's review have been excluded from this table as the original reports are not in english . 
   table 1inguinal lymph node metastases from adamantinoma of the tibia as reported in the english literature ( pub med , medline , scopus , embase , google / google scholar ) since 1930-search terms included adamantinoma of the tibia , and tibial adamantinoma and metastases , and inguinal lymph node metastases.reference numberyear reportedauthorsexage at diagnosisbone involvedlocation in bonecharacter and duration of symptoms + /history of traumalatent periodtreatmentoutcome#101938dunnem32left tibiaupper and middle thirdsswelling , 4yr ; pain later months severe contusionnine monthshigh voltage roentgen , ak amputation 9 months laterdied , 8 years inguinal lymph nodes*#111942dockerty , meyerdingf24left tibiamiddlerecurrent pain , 8 yr . , swelling , 4yr . 
   no history of traumanonelocal excision , ak amputation 15 months laterdied , 1 year , inguinal lymph node metastases#121952mangalik , lal mehrotram40femur , tibia , fibuladistal proximal middleduration of symptoms for 12 months . 
   previous injury to leg1 yearak amputation , irradiation of metastatic nodes#131962knappf14left tibiamiddlemass for 4 years no history of traumaak amputationtotal survival 16 years . 
   pulmonary and inguinal lymph node metastasis#141976winter wgm30left tibiadistalnoneresection , disarticulation of lk , inguinal node dissection , pleurectomydied with inguinal nodes , pulmonary , brain - right occipital metsm37tibiamiddlenoneresection and bone grafting very late knee disarticulationdied , 8 years after initial surgery inguinal lymph nodes and pulmonary metastasis#151990de keyserf13tibiapathological fractureintramedullary nailing several curettages , en bloc resection bk amputation , ak amputationdied 4 years after ak amputation had pulmonary and lymph node metastasis#61994hazelbagm26left tibiadistalnoneamputation metastasis to groin lymph node , pelvisdied of diseasem15left tibiadistalnonechemotherapy , amputationdied of disease . 
   lung / lymph metastases#162008freym20tibianadnadtotal tibia allograft knee disarticulation polychemotherapypulmonary and inguinal lymph node metastases amputation2011tharmabala et al.f24left tibiaswelling left tibia swelling in left groin4 yearssurgical excision in left tibia 2004 . 
   left retroperitoneal mass excision 2009left inguinal nodal metastasis , stable pulmonary nodules with routine follow up in 2011*this is reported in reference # 17 by moon in 1965 . 
   it was first described by maier in 1900 as a primary bone tumor with epithelial characteristics . later in 1913 , fischer named the tumor primary adamantinoma of the tibia because of its resemblance to adamantinoma ( also known as ameloblastoma ) of the jaw and the pituitary gland . 
   although , adamantinoma of the tibia histologically resembles adamantinomas of the jaw and pituitary , there has been no evidence to suggest that these tumors are of similar origin . 
   adamantinoma has also been associated with osteofibrous / fibrous dysplasia and in this regard is considered by some authors to represent a spectrum of disease with evidence of progression from osteofibrous / fibrous dysplasia to adamantinoma in some cases . due to the rarity of this lesion and the varied histological phenotypes , adamantinoma of the tibia 
   can be a diagnostic dilemma leading to misdiagnosis , delay , and suboptimal treatment , as seen in our cases . 
   it can present at any age but mostly occurs in the second to fourth decade . 
   they are most commonly ( 8590% ) localized in the tibial diaphysis rarely , it has been described in other bones of the appendicular skeleton including the fibula , ulna , femur , humerus , radius , and short bones of the feet . 
   , , adamantinoma of the tibia can be divided into two main groups based on their histology and biological behavior . 
   classical adamantinoma refers to the prototype cases with a predominance of epithelial tumor cells and are associated with a destructive growth pattern on radiology . 
   patients with classical adamantinoma are usually of an older age group with a reported range of 1565 years . 
   this variant of classical adamantinoma has a stronger predisposition to local recurrences and a higher potential for distant metastases . 
   in contrast , differentiated adamantinoma of the tibia has a predominance of a osteofibrous / fibrous dysplasia like pattern with scant epithelial tumor elements and is commonly seen in an intracortical location . 
   many authors suggest that osteofibrous/ fibrous dysplasia , a benign lesion occurring commonly in the tibia of children under 10 years of age , is related to adamantinomas and may even be a precursor lesion for adamantinomas . 
   , in such scenarios , tibial adamantinomas have often been misdiagnosed as fibrous dysplasia , as seen in our case . 
   the association of fibrous dysplasia with adamantinoma was first described by cohen et al . in 1962 who proposed that the fibrous pattern seen in such cases was different from that seen in classical fibrous dysplasia . 
   this variant of differentiated adamantinoma is considered by some authors as a secondary reparative process that is associated with a more benign behavior and better prognosis . 
   distant metastases have been reported in adamantinoma of the long bones in about 1520% of cases this may be falsely low due to the slow growing nature of the tumor as long term follow up is required to evaluate its true metastatic potential . 
   regional or other distant metastases as seen in the lung are found more frequently in patients who have a history of repeated local recurrences linked to inadequate primary excision of this lesion . 
   however , in our case ( case 1 ) inguinal nodal metastases occurred with no evidence of local recurrence . 
   risk factors for metastases include male sex , persistent pain , symptoms of less than five years duration , and inadequate initial treatment by biopsy curettage / excision , or resection . 
   the only histological feature associated with an increased recurrence rate was lack of squamous differentiation . in view of the relationship between adamantinoma and osteofibrous dysplasia , czerniak et al . proposed two biological courses that a tibial adamantinoma may follow . 
   one is by the differentiated adamantinomas , which are predominantly intracortical and behave as a reparative process with a low potential to metastasize . 
   the second , such as that seen in our case ( case # 2 ) of classical adamantinoma , is one of progressive tumor growth with a higher potential to metastasize . 
   early metastases within the first two years of initial diagnosis is commonly seen to occur to the regional lymph nodes , whereas delayed metastases is almost always pulmonary or osseous . 
   given that lymph node metastasis usually occurs within the first two years , this is suggestive that these were present at the time of initial diagnosis . in this context , we recommend ultrasound imaging of regional lymph nodes as an essential component in the follow - up examinations of these cases . 
   the current practice recommends surgical extirpation as the primary mode of treatment for localized regional lymph node metastases with radiotherapy and chemotherapy as suggested alternatives . 
   the exact role for sentinel node biopsy and its cost / benefit ratio is unknown due to limited clinical experience in these rare lesions . in conclusion , 
   tibial adamantinoma is a rare primary bone tumor that can cause diagnostic dilemmas especially with clinical presentations of the uncommon pattern of regional nodal metastases . 
   increased clinical awareness of such rare neoplasms with recognition of uncommon patterns of metastases is essential for accurate diagnosis and optimal patient management . 
   additionally , due to the slow - growing nature of tibial adamantinomas we recommend continuous long - term follow up for these patients .
summary: adamantinoma is a rare primary bone tumor that commonly arises in the jaw and has also been described in the appendicular skeleton such as the tibia . 
   we report 2 cases of tibial adamantinomas that were originally misdiagnosed ; one as fibrous dysplasia of the tibia and the other as a cutaneous eccrine carcinoma in a groin mass , which was metastatic adamantinoma to the inguinal lymph nodes . 
   such metastatic adamantinoma to the groin lymph nodes is extremely rare . 
   the clinical and pathological data with a review of the available literature on inguinal lymph node metastases from primary tibial adamantinoma are reported . 
   increased clinical awareness and accurate recognition of such uncommon patterns of inguinal nodal metastases are imperative for appropriate planning of therapeutic strategies and risk management in these patients .