benign schwannoma is a slow growing encapsulated tumor arising from the neuroectodermal sheath of schwann .
approximately , 25 - 30% of all reported schwannomas occur in the head and neck and most of these in the eighth nerve .
schwannoma of the facial nerve is a rare entity with very few cases reported in the literature . in our case
a 7-year - old female was brought to ent out - patient department with right - sided parotid swelling of 1-year duration .
initially , the swelling was small in size that gradually and painlessly increased up to its present size [ figure 1 ] .
the swelling was 10 cm  9 cm  7 cm in size , firm in consistency , had bosselated appearance , was mobile horizontally and vertically and the skin over the swelling was mobile .
cytology was advised , and it came out to be a benign parotid tumor . since the mass was large in size and patient was a child , a computed tomography ( ct ) scan
ct scan suggested a well - defined , lobulated , homogenous , mildly enhancing soft tissue lesion with loss of interface with the masseter muscle and multiple small lymph nodes [ figure 2 ] .
a provisional diagnosis of pleomorphic adenoma was made , and superficial parotidectomy planned [ figure 3 ] .
peroperatively , the facial nerve trunk was found deeper and inferior due to pushing effect of the tumor . however , on further anterior dissection the tumor was found to originate from the buccal and zygomatic branches of the facial nerve .
the patient had postoperative ( after 3 months of surgery ) facial weakness of grade three ( house brackmann classification ) [ figure 4 ] .
female patient with right parotid swelling ( preoperative ) computed tomography scan showing the parotid mass line of incision of the planned surgery postoperative photograph showing facial weakness the gross appearance of the tumor was like a brain tissue [ figure 5 ] and histopathologically , it was confirmed to be an intraparotid shwannoma , showing antoni type a and b cells [ figure 6 ] .
the lymph node showed reactive changes . resected tumor resembling brain tissue histopathological slide showing salivary and nervous tissue
among 802 parotid tumors reported eneroth and hamberger could demonstrate two cases with neurogenic origin and in a review of 700 parotidectomies nussbaum et al . found only one case of neurilemma of the facial nerve .
the intraparotid facial nerve shwanommas are mostly ( 75% ) asymptomatic . the tumor grows eccentrically pushing the nerve fibers away as observed in the present case . the ability of the parotid to accommodate the expanding tumor results in facial nerve palsy in only 20 - 27% of cases . in some cases , radiology may provide preoperative information about facial nerve schwannoma but in many cases it mimics pleomorphic adenoma . the ct scan although not the preferred method of imaging shows a smooth and sharply defined mass in the parotid .
fine - needle aspiration cytology is also unreliable for diagnosing these lesions as in most cases results are inconclusive or suggest a pleomorphic adenoma .
the diagnosis is , therefore , generally made peroperatively when the surgeon finds difficulty in identifying the facial nerve . in our case , the size of the tumor was quite big and could have complicated into facial nerve palsy very soon .
moreover , the patient 's preference to get the tumor operated was the main indication for a surgical intervention .
any parotid mass in children should be viewed with suspicion and adequately investigated before any intervention is planned .
intraparotid schwannoma should be suspected if the facial nerve can not be found intraoperatively , if the tumor is intimately associated with the facial nerve and if the gross appearance of the tumor is like that of a brain tissue . in cases where schwannoma is suspected , biopsy is recommended while complete resection is postponed to obtain imaging studies to evaluate the extent of disease and to discuss possible outcomes with the patient .
 pleomorphic adenomas are the most common tumors which present as parotid masses . 
 shwannoma ( peripheral nerve sheath tumor ) is a rare entity in this region . 
 very few schwannomas originate from the facial nerve and in the majority of these cases the tumor involves its intratemporal part . 
 the following case is reported because it presented as an asymptomatic parotid swelling with normal seventh nerve function , which masqueraded as pleomorphic adenoma clinically , radiologically and cytologically . 
 however , it turned out to be peripheral nerve sheath tumor on histopathological examination . 
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