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schwannomas are infrequent benign neoplasms arising from cranial , peripheral or autonomic nerves that contain schwann cells .
the prognosis is very good since they do not usually recur , and malignant transformation is rare .
about 25 - 45% of schwannoma occur in the head and neck ; only 1% have an intra - oral origin .
the tongue is the most common site ; its location in the palate is rare .
we report a case of schwannoma of the hard palate with bony erosion , which was excised intra- orally and after two months the defect was completely covered with palatal mucosa .
a 28-year - old man presented with a gradually increasing swelling over the palate for four years ; pain in the swelling was for last three months . on examination ,
the swelling was over the hard palate , more towards the left side , it was 3 cm in diameter with a small ulcer having purulent discharge [ figure 1a ] .
the mucosa over the mass was normal except a whitish spot at the discharge point .
( a ) the lesion over the hard palate ; ( b ) bony erosion of the hard palate in cect ; ( c ) excised specimen , oral side ; ( d ) cut section of excised specimen there was no medical history of interest . clinical diagnosis at that time was minor salivary gland tumor .
fine needle aspiration cytology revealed benign squamous cells and a single cluster of spindle cells with bland nuclear features .
contrast - enhanced computed tomography showed irregular thickening at the left side of the anterior hard palate with central hypodense area .
on careful dissection it was found that the bony palate at its base was destroyed .
on cut section there was whitish tumor with focal hemorrhage [ figure 1c and d ] .
microscopic examination showed an encapsulated tumor composed of fascicles of spindle cells exhibiting alternate cellular and hypocellular areas ( antoni a and antoni b ) .
with immunohistochemistry ( ihc ) , s-100 was positive and smooth muscle antigen ( sma ) was negative in the tumor cells .
schwannoma with antoni a and antoni b areas , h and e , 100 ; inset - s100-positive tumor cells , 100 postoperative period was uneventful .
the term schwannoma was originally suggested because this neoplasm was thought to be derived from schwann cells of peripheral nerve sheaths .
these cells were named after german anatomist , physiologist , and cofounder of the cell theory , theodor schwann ( 1810 - 82 ) . in 1908 ,
neurinoma. in 1935 , arthur stout coined the term  neurilemmoma. in 1940 , on the basis of light microscopic studies , isadore max tarlov proposed this tumor to be of fibroblastic origin and coined the term  perineural fibroblastoma. today , most pathologists consider the terms schwannoma , neurinoma , neurilemmoma , and perineural fibroblastoma to be synonymous and distinguish this lesion from neurofibroma . according to erlandson ( 1985 ) , schwannomas may be : classical ( verocay ) , cellular , plexiform , cranial nerve , melanotic , degenerated ( ancient ) , and granular cell types .
about 25 - 45% of schwannomas occur in the head and neck , and only 1% demonstrate an intraoral origin , being found principally in the anterior portion of the tongue .
a review of the literature on hard - palate schwannomas was done ; the results are shown in table 1 . in this study ,
there was a wide range of age distribution , second to sixth decade of life ( mean age , 36.2 years ) .
schwannomas of the head and neck region can occur at any age , and are most commonly found during the second and third decades of life .  
comparison of present case of schwannoma of hard palate ( pathological proven ) with that of other cases in the literature gender distribution of head and neck schwannomas varies in different studies .
it was a painless , sessile mass in all cases , and pedunculated in one .
all these schwannomas measured between 1.5 and 5 cm in greatest dimensions ( mean , 2.64 cm ) .
the duration of clinical presentation of the schwannomas was from 3 months to 15 years .
there are three mechanisms by which schwannomas may involve bone : ( 1 ) they may arise centrally within bone , ( 2 ) they may arise within the nutrient canal and produce canal enlargement , or ( 3 ) a soft tissue or periosteal tumor may cause secondary erosion and penetration into bone . clinically ,
two forms of oral schwannomas can occur : the most frequent is the encapsulated type , in which the tumor is surrounded by dense fibrous connective tissue ; the other is the pedunculate type , resembling a fibroma .
it is believed to originate from proliferation of schwann cells in the perineurium causing displacement and compression of adjacent nerve .
it does not arise from cranial nerve i and ii because they lack schwann cells .
the preoperative diagnosis is quite difficult , among other reasons because this is an infrequent tumor and is not usually suspected in the oral cavity . in the reviewed cases
computed tomographic or magnetic resonance imaging scans can be useful in the initial workup to determine the extent of the lesion and assist with delineating a differential diagnosis .
histologically , neurilemmomas are composed of two distinct areas termed as antoni a and antoni b regions .
the structure as a whole , including a central stromal region , is known as a verocay body . by comparison ,
the antoni b regions are loose and hypocellular , and the schwann cells appear polymorphic . on ihc , s-100 protein shows strong positivity for neurilemmomas , reflecting their propensity of schwann cells .
we can conclude that the possibility of schwannoma should be kept in mind when dealing with an intraoral , well - circumscribed , soft - tissue lesion .
schwannomas are benign encapsulated perineural tumors . 
 the head and neck region is the most common site . 
 intraoral origin is seen in only 1% of cases , tongue being the most common site ; its location in the palate is rare . 
 we report a case of hard - palate schwannoma with bony erosion which was immunohistochemically confirmed . 
 the tumor was excised completely intraorally . 
 after two months of follow - up , the defect was found to be completely covered with palatal mucosa .