low - grade fibromyxoid sarcoma ( lgfms ) is a distinctive variant of fibrosarcoma , which was first described as a pathologic entity by evans in 1987 .
lgfms presents as a rare soft tissue tumor with a high metastasizing potential , despite the benign histologic appearance
. these tumors usually occur in the lower extremities , followed by the trunk , groin , upper extremities , thorax , buttocks and abdominal wall ; the maxillofacial region being rarely involved .
the vast majority of lgfms occur in a subfascial location ; rarely , the subcutis or dermis may be affected .
lgfms typically involves young or middle - aged adults , but a large number of pediatric cases have also been reported . here ,
a 35-year - old male patient reported to the department of oral medicine and radiology with a complaint of swelling in the mandibular left posterior region since 6 months [ figure 1 ] .
history revealed that it was initially peanut sized , 6 months back but had gradually increased to the present size .
there was no history of pain , trauma , paraesthesia or anesthesia , or pus discharge associated with the swelling . on examination
, there was a solitary well - defined sessile swelling seen on the left body of the mandible , measuring approximately 3 cm  2 cm in dimension .
the swelling was nontender , firm in consistency , noncompressible , nonfluctuant and possessed no mobility .
intraoral examination revealed a mild vestibular obliteration in the region of 34 , 35 and 36 [ figure 2 ] .
root stumps were present in relation to 18 , 27 and 37 . based on the clinical findings ,
the differential diagnoses considered were peripheral nerve sheath tumor , soft tissue fibroma and soft tissue sarcoma .
extra orally , a well - defined ovoid sessile swelling seen on the body of the mandible on the left side intra oral examination revealed vestibular obliteration in the region of 34 , 35 and 36 and root stumps in relation to 37 orthopantomograph showed root stumps in relation to 37 and a subtle change in the trabecular pattern in the periapical region of 35 , 36 and 37 [ figure 3 ] .
occlusal radiograph showed a well - defined soft tissue outline of the tumor on the buccal aspect with erosion of the buccal cortex in the region of 35 [ figure 4 ] .
cropped orthopantomograph showed root stumps wrt 37 and a subtle change in the trabecular pattern in the peripaical region of 35 , 36 and 37 occlusal radiograph showed a well - defined soft tissue outline of the tumour on the buccal aspect with erosion of the buccal cortical plate in the region of 35 ultrasonography ( usg ) revealed an ill - defined hyperechoic soft tissue lesion in the deep planes of the left submandibular region abutting the body of the mandible .
the tumor revealed ill - defined margins with erosion of the underlying bone and insignificant vascularity .
marginally enlarged lymph nodes were noted in the left cervical region , largest measuring 1.1 cm in dimension . computed tomography ( ct ) showed a well - defined encapsulated fusiform soft tissue mass with a density of 2030 hu measuring 3 cm  1.8 cm  2.8 cm adjacent to the left body of the mandible .
there was minimal appreciable enhancement and the tumor was causing scalloping of the adjacent bone with thinning of the buccal cortex [ figure 5 ] . computed tomography
showed a well - defined encapsulated fusiform soft tissue mass with a density of 2030 hu , minimal appreciable enhancement , causing scalloping of the adjacent bone and thinning of the buccal cortex based on the radiological features , a diagnosis of benign nerve sheath tumor was made .
histopathological examination of core biopsy revealed loosely arranged fascicles of spindle cells with loose myxoid stroma .
the features were suggestive of a benign nerve sheath tumor . surgical excision of the tumor was done under general anesthesia .
the tumor was seen encasing the mental nerve which was subsequently resected at the level of the mental foramen [ figure 6 ] . cut section of the tumor showed a solid , gray - white mass with myxoid areas [ figure 7 ] .
the mental nerve was resected at the level of the mental foramen cut section shows solid , gray - white mass with myxoid areas histopathological examination showed a myxoid tumor with hypocellular areas in nodules merging with collagenised areas .
immunohistochemical analysis showed strong positivity for vimentin and negativity for s100 protein , desmin , smooth muscle actin ( sma ) , cd34 , cd31 , cd68 , cytokeratin ( ae1/ae3 ) and epithelial membrane antigen ( ema ) [ figures 9 and 10 ] .
based on the histopathological and immunohistochemical findings , a final diagnosis of lgfms was given .
bland spindle cells with no atypia in short fascicles and whorls in the myxoid zone ( h&e stain , 40 ) positivity of vimentin in tumour cells ( ihc stain , 100 ) s100 negative in tumour cells ( ihc stain , 40 )
lgfms is a rare soft tissue neoplasm described first by evans in 1987 . in his original paper , evans had described the tumor histopathologically as a bland appearing soft tissue neoplasm associated with aggressive behavior and high degree of local recurrence or local metastasis . in his second paper in 1993 , evans reported 12 cases of lgfms , of which nine patients had local recurrence and seven patients experienced distant metastasis and died from lgfms .
folpe et al . in 2000 , described 54 cases of lgfms and reported that only 9% of the cases showed local recurrence and 3% showed distant metastasis .
the tumor mainly affects the young and middle - aged with an age range of 2050 years having no gender predilection .
the most frequent sites of occurrence of this tumor are the lower extremities , followed by the trunk and groin , upper extremities and buttocks .
lgfms involving the maxillofacial region is a very rare entity with only six cases reported in english literature till date [ table 1 ] .
reported cases of low grade fibromyxoid sarcoma in the maxillofacial region it is extremely difficult to make a diagnosis of lgfms before surgical intervention because of the relatively benign clinical nature and nonspecific findings of imaging modalities such as usg , ct and magnetic resonance imaging ( mri ) .
contrast enhanced ct shows heterogeneous enhancement , but sometimes the enhancement is not obvious , as in our case .
mri shows homogeneous signal intensity similar to muscle on t1-weighted images and heterogeneous low to high signal intensity on t2-weighted images .
morphologic and molecular overlap of hyalinizing spindle cell tumor ( hsct ) with giant rosettes and sclerosing epithelioid fibrosarcomas with lgfms suggests the possibility of considering them as variants .
evans described the typical histological findings of lgfms as contrasting fibrous and myxoid areas with moderate to low cellularity , deceptively benign - appearing spindle cells with no or slight nuclear pleomorphism and rare mitotic figures and a swirling , whorled growth pattern .
in addition to these features , two cases of lgfms with heterotopic ossification and giant rosettes have also been reported .
although there is no specific marker for lgfms immunohistochemistry is essential to exclude the possibility of tumors with similar histopathologic findings .
muc4 is now considered highly specific and quite sensitive marker helpful in distinguishing lgfms from mimics .
markers including s100 , sma , desmin , cd34 , cd31 , cd68 , ema and cytokeratin ( ae1/ae3 ) have been used to distinguish between a number of tumors .
hsct presents with varying number of large , rosette - like structures which arise from hyalinization zones or emerge abruptly from the spindled stroma .
on immunohistochemistry , both the entities are strongly positive for vimentin , but there are differences between hsct and lgfms for other antibodies .
investigators have reported that giant rosettes of hsct are positive for s100 , occasionally positive for cd34 , leu-7 and neuron - specific enolase and negative for desmin , sma and ema .
in contrast , the tumor cells of lgfms are occasionally positive for desmin , sma , ema and cd34 but are negative for s100 , leu-7 and neuron - specific enolase . an important cytogenetic tool which will be helpful in the diagnosis of both these
has been the recognition of a characteristic balanced translocation t(7 ; 16 ) ( q34:p11 ) and the finding of a novel fusion gene fus / creb3 l2 .
techniques include local excision , radical surgery , wide en bloc resection , compartmental resection .
the role of chemotherapy and radiotherapy as adjuncts to surgical intervention is unclear . in a study conducted by tang et al . in 2010 ,
data of 273 patients diagnosed with hsct or lgfms were collected , of which follow - up data were available for 184 patients .
local recurrences and distant metastases were observed in 54 ( 29.34% ) and 34 ( 18.48% ) patients , respectively .
metastasis was seen mainly in the lung followed by other soft tissues and very rarely in bone . due to the relatively high local recurrence rate and late metastasis ,
lgfms is a very rare low - grade malignancy occurring in the maxillofacial region , with nonspecific histopathological findings .
diagnosis is not possible with clinical and imaging studies , rather a meticulous histopathological , immunohistochemical examination and cytogenetics is required to arrive at a diagnosis , differentiating from its mimics .
long - term follow - up is required in the management of these cases because of late metastasis and high recurrence rate .
 low - grade fibromyxoid sarcoma ( lgfms ) is a distinctive variant of fibrosarcoma with a high metastasizing potential and is characterized by a long interval between tumor presentation and metastasis . 
 lgfms involving the maxillofacial region is a very rare entity with only six cases reported till date . 
 lgfms is characterized by its benign histological appearance , with spindle cells in whorling pattern , and collagenized and myxoid areas . 
 the heterogeneous histological appearance makes the diagnosis challenging . 
 immunohistochemical staining has been reported by a number of authors , with some conflicting results , showing positivity with vimentin , but no immunoreactivity with antibodies to keratin , desmin , actin , s100 or epithelial membrane antigen . 
 we present a case of a 35-year - old male patient who developed a mass on the left mandibular body region . 
 the tumor was excised along with mental nerve at the level of the mental foramen . 
 the tumor on pathologic and immunohistochemical evaluation was diagnosed as lgfms . 
INTRODUCTION
CASE REPORT
DISCUSSION
CONCLUSION
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