a 10-week - old boy presented with a history of rapidly progressive swelling over the left upper alveolus of a few weeks duration .
the past medical and obstetric history was unremarkable and there was no history of trauma .
physical examination revealed a healthy infant with a reddish - bluish , firm , fixed and non - tender orofacial swelling involving the left upper vestibule and anterior hard palate , crossing the midline towards the right side ( fig .
figure 1orofacial swelling involving the left upper vestibule , alveolar margin and anterior hard palate .
computed tomography ( ct ) and magnetic resonance ( mr ) scans were done to evaluate the lesion .
a ct examination of the face was done on a multi - detector computed tomography ( mdct ) scanner ( emotion duo ; siemens medical systems , erlangen , germany ) .
contrast - enhanced scans were obtained after manual intravenous injection of 20  ml of nonionic iomeprol ( iomeron-300 , bracco , ferentino , italy ) containing 300  mg / ml iodine .
the ct scan revealed a bilobular , expansile bone lesion with homogenous soft - tissue density content , involving the anterior maxilla and adjacent hard palate , and displacing the developing dentition ( fig .
figure 2axial contrast - enhanced ct scan images in ( a ) soft - tissue window and
( b ) bone window settings show an expansile , bilobed , well - circumscribed , solid lesion with epicenter in the anterior maxillary alveolar ridge .
axial contrast - enhanced ct scan images in ( a ) soft - tissue window and
( b ) bone window settings show an expansile , bilobed , well - circumscribed , solid lesion with epicenter in the anterior maxillary alveolar ridge .
an mr scan of the face was done on a 1.5-tesla scanner ( avento ; siemens medical systems , erlangen , germany ) .
( t2w ) turbo spin echo sequences were obtained in multiple planes with 3-mm - slice thickness .
contrast - enhanced t1-weighted turbo spin echo scans were obtained after intravenous injection of 0.1  ml / kg of gadobenate dimeglumine ( multihance , bracco , milan , italy ) .
the mri scan revealed a bilobular bone lesion with lobulated margins and internal soft - tissue content involving the anterior maxillary alveolar margin and adjacent hard palate .
the lesion showed hyperintense signals on t1w images and mildly hyperintense signals on t2w images ( fig .
figure 3mr axial ( a ) t1-weighted , turbo spin echo , 630/17 , ( b ) t2-weighted , turbo spin echo 4400/72 , ( c ) gadolinium - enhanced t1-weighted turbo spin echo images .
images demonstrate a well - defined bilobed , solid , homogenous mass centered at the anterior maxillary ridge .
the mass is hyperintense to muscles and tongue on both t1w ( a ) and t2w ( b ) images , contrary to the expected findings of melanin pigment .
mr axial ( a ) t1-weighted , turbo spin echo , 630/17 , ( b ) t2-weighted , turbo spin echo 4400/72 , ( c ) gadolinium - enhanced t1-weighted turbo spin echo images .
images demonstrate a well - defined bilobed , solid , homogenous mass centered at the anterior maxillary ridge .
the mass is hyperintense to muscles and tongue on both t1w ( a ) and t2w ( b ) images , contrary to the expected findings of melanin pigment .
a core needle biopsy revealed small round cells with peripherally arranged larger pigment - containing cells in alveolar distribution lying in fibrous stroma ( fig .
a full panel of immunohistochemistry markers were run on the biopsy tissue , which was strongly reactive for cytokeratin ( ck ) , hmb45 and neuron - specific enolase ( nse ) and negative for s-100 , cd99 and leukocyte common antigen ( lca ) , confirming the diagnosis of melanotic neuroectodermal tumor of infancy ( mnti ) ( fig .
figure 4histopathological image ( magnification 300 ; hematoxylin and eosin stain ) of the excised mass showing a nest of small cells ( small arrow ) and larger melanin - containing cells ( large arrow ) in a fibrous stroma ( open arrow ) . 

figure 5immunohistochemical assay images showing marked uptake of ( a ) ck , ( b ) hmb45 and ( c ) nse .
histopathological image ( magnification 300 ; hematoxylin and eosin stain ) of the excised mass showing a nest of small cells ( small arrow ) and larger melanin - containing cells ( large arrow ) in a fibrous stroma ( open arrow ) .
immunohistochemical assay images showing marked uptake of ( a ) ck , ( b ) hmb45 and ( c ) nse .
the excised specimen was a bluish - black oval mass consistent with a pigment - containing tumor ( fig .
figure 6image of the extirpated specimen showing an oval mass with bluish - black pigmented areas .
image of the extirpated specimen showing an oval mass with bluish - black pigmented areas .
mnti was first described by krompecker in 1918 ; he called it congenital melanocarcinoma . since then , there has been uncertainty about its cellular origin .
the origin presumed earlier was from odontogenic or retinal rests , and this led to a plethora of names such as retinal anlage tumor , pigmented ameloblastoma , melanotic adamantinoma , retinal choristoma , melanotic epithelial odontoma , melanotic progonoma , pigmented teratoma , atypical melanoblastoma , pigmented epulis and retinoblastic teratoma .
however , based on immunohistochemical , ultrastructural , and electron microscope studies and on occasional high urinary excretion of vanillylmandelic acid ( vma ) , it is now agreed that the tumor originates from the neural crest .
therefore , the tumor is most commonly referred to as a melanotic ( melanocytic ) neuroectodermal tumor of infancy , a term first coined by borello and gorlin in 1966 .
. it may be locally aggressive in 1536% of cases ; 37% of tumors have an overtly malignant behavior with distant metastases .
mtni usually ( 95% ) occurs in children less then 1 year of age peaking between 2 and 6 months , although occasionally it has been described in adults .
the tumor usually occurs in the head and neck region because of its origin from the neuroectoderm .
anterior maxilla ( premaxilla ) is the most common site of origin , occurring in almost 71% of cases .
rarely , it can arise in the skull , mandible , brain , meninges , transverse sinus , retina , mediastinum , bones , soft tissue , uterus , and epididymis . in the skull ,
the anterior fontanelle is the most common site ; the epididymis is the most common extracranial site .
the classic clinical presentation is a sessile , firm swelling involving the upper anterior alveolar ridge and anterior hard palate .
the presence of melanin gives it a bluish hue , often mimicking a vascular malformation .
it may result in facial asymmetry , dentition displacement and difficulty in feeding . on gross examination ,
two groups of cells are noted with larger pigment - containing melanocyte - like cells arranged in an alveolar pattern between the fibrovascular septae and smaller non - pigmented neuroblast - like cells dispersed in the center of nests .
histopathologic examination is usually unreliable to differentiate benign from malignant changes as cellular atypia and sparse mitosis may be seen even in benign lesions .
immunohistochemistry is characteristic , being strongly reactive to cytokeratin , hmb45 , synaptophysin , nse , epithelial membrane antigen , glial fibrillary acidic protein and leu-7 , but negative for s-100 protein .
electron microscopy shows ultrastructural findings typical of neural , epithelial and melanocytic cells , such as the presence of intracellular melanosomes in various stages of development , numerous intercellular junctions , neurofibrils and desmosomes .
pathological differential diagnosis would include other small round cell tumors such as neuroblastoma , ewing sarcoma , rhabdomyosarcoma , lymphoma , primitive neuroectodermal tumor , etc .
the plain radiograph of mnti shows a well - circumscribed , radiolucent , expansile lesion involving the anterior maxilla .
the mass appears as an expansile bone lesion centered at the anterior maxilla , with a thin continuous bone shell and internal soft - tissue density content that enhances on intravenous contrast .
bone expansion , erosion , hyperostosis and spiculations can all be seen in the same lesion .
mr imaging findings should follow the paramagnetic effect of its melanin content , that is , the characteristic hyperintense signals on t1w images and hypo- to iso - intense signals on t2w images .
the enhanced t1 relaxation ( shortened ) of melanin is probably due to chelation of paramagnetic metal ions by melanin .
the enhanced ( shortened ) t2 relaxation is explained by melanin - induced heterogeneity in the magnetic susceptibility of the surrounding environment , resulting in rapid t2 decay .
however , this typical mr signal pattern of melanin is only seen in very densely pigmented tumors , and when present can often clinch the diagnosis in an appropriate clinical setting . more often than not and as in our case , the mr signals are unlike a melanin signal , because of the variable proportion of melanin in the predominantly non - melanin content .
multiple foci with variable signals representative of melanin , bone and soft tissue can be seen within the same tumor .
melanin signals may be mimicked by a paramagnetic effect of methemoglobin or a highly cellular tumor .
the differential diagnosis of mnti includes : ( 1 ) developmental cysts ( nasopalatine cyst , globulomaxillary cyst ) ; ( 2 ) odontogenic lesions ( odontoma , ameloblastoma , ameloblastic fibroma , odontogenic myxoma , adenooameloblastoma , odontogenic keratocyst ) ; ( 3 ) non - odontogenic non - neoplastic lesions ( central giant cell granuloma , fibrous dysplasia and arteriovenous malformation ) ; and ( 4 ) non - odontogenic neoplastic lesions ( rhabdomyosarcoma , burkitt lymphoma , langerhans cell histiocytosis , ewing sarcoma ) .
however , this long list can be reduced to just a few based on the clinical and radiological features .
management is usually by wide surgical excision with at least 5  mm of healthy margins . in the absence of free margins ,
the recurrence rate is increased by five times , most of which occur within 4 months and local radiotherapy with combination chemotherapy is then recommended .
delayed recurrences can be seen which makes close post - operative follow - up essential in all cases . in summary ,
mnti , although rare , has a distinctive clinicopathological and imaging features and it should be considered in the differential diagnosis of all patients presenting with head and neck masses particularly if present in the maxillary region .
 abstractmelanotic neuroectodermal tumor of infancy ( mnti ) is an uncommon melanin - containing mesenchymal tumor of neural crest origin . 
 what make this tumor unique and interesting is its characteristic predilection for anterior maxilla ( premaxilla ) and the presence of pigment melanin which gives the tumor distinct clinicopathological , immunohistochemical , ultrastructural and imaging features . 
 although first described almost a century ago , to the authors knowledge , only a few hundred cases of mnti have been reported worldwide in the english medical literature . 
 the pool of documented radiological findings is even more sparse as not more than a dozen cases could be abstracted from an internet search of the radiology literature . 
 we document a case of mnti and describe the imaging findings with intent to contribute to its small but accruing radiological data . 