pediatric soft - tissue sarcomas ( stss ) account for approximately 7% of all childhood tumors . out
though surgery is the mainstay of treatment , advent of neoadjuvant chemotherapy ( nact ) has reduced the incidence of recurrence / metastasis .
we present a case of ifs with early and unusual distant metastasis , localized on fluorodeoxyglucose positron emission tomography - computed tomography ( fdg pet - ct ) scan .
the patient , a 4-year - old girl child , is a known case of ifs , primarily involving right proximal tibia and staging whole body pet / magnetic resonance ( mr ) scan not suggestive of disease elsewhere .
she was detected with local relapse 3 months later for which she underwent chemotherapy followed by right above knee amputation .
on physical examination , she had a palpable mildly tender lump in right proximal thigh .
an mr imaging of the right thigh was obtained , which showed a neoplastic lesion involving right proximal shaft of femur .
the maximum intensity projection [ figure 1 ] was suggestive of significant tracer uptake in right facial , lower lumbosacral , and bilateral proximal thigh regions .
the axial ct and fused pet - ct images demonstrated fdg avid hypermetabolic foci in soft - tissue lesions involving right zygoma with intraorbital extension ( maximum standardized uptake value [ suvmax 9 ] ) [ figure 2a ] , right proximal femur [ suvmax 6.1 , figure 2b ] , sacrum with involvement of right sacroiliac joint [ suvmax 16 , figure 2c ] , and right suprascapular region [ suvmax 9 , figure 2d ] .
maximum intensity projection of f-18 fluorodeoxyglucose positron emission tomography - computed tomography showing increased tracer uptake in regions pointed by arrowheads transaxial computed tomography and fusion positron emission tomography - computed tomography images on f-18 fluorodeoxyglucose positron emission tomography - computed tomography scan showing fluorodeoxyglucose avid hypermetabolic foci in soft - tissue lesions involving ; ( a ) right zygomatic bone with intraorbital extension , ( b ) right proximal femur , ( c ) sacrum and right sacroiliac joint , and ( d ) right suprascapular region subsequently , biopsy was obtained from sacral and right proximal femoral lesions .
the tumor cells were arranged in interlacing fascicles and herringbone pattern [ figure 3a ] , with pleomorphic nuclei and brisk mitotic activity of > 10/10 hpf .
microscopic images of hematoxylin and eosin stained biopsy slides obtained from sacral and right proximal femur lesions showing ; ( a ) arrangement of tumor cells in interlacing fascicles and herringbone pattern , with ( b ) multiple blood vessels dispersed within the tumor tissue
ifs has incidence of 5 per million in the pediatric age group and majority of the patients are < 2 years old .
although its etiology is unknown , a fusion transcript etv6-ntrk3 resulting from a chromosomal translocation t(12;15 ) is commonly associated .
the extremities account for the primary in almost 74% of the cases , followed by head and neck region .
most common site of origin is around knee joint followed by thigh and hip regions .
the pathologic appearance of ifs includes spindle cells with many blood vessels arranged in hemangiopericytoma - like fascicular pattern .
advent of nact allowed conservative surgeries and decreased local as well as metastatic relapses . in a large study comprising 56 infants by orbach et al .
seventy - three percent of these were found to be chemosensitive and 22% maintained stable disease .
performed a retrospective study with 11 patients who were treated with surgery alone or nact + surgery .
rest , all were followed up for varying periods of 18 months to 13.5 years and were found to be disease free .
three patients who had primary in extremities achieved complete remission and were disease free even after 2 years of follow - up .
one infant had a neck primary and developed metastases to brain , lungs , and kidneys , which responded to chemotherapy .
in addition , studies have proved that ifs carries overall 5-year survival rate of > 85% .
overall , 1743% of cases present with local recurrence within 1 year after curative treatment .
further , ifs originating from extremities is found less likely to cause distant metastases ( 8% ) than axial ifs ( 26% ) . who classification of stss categorizes ifs in intermediate rarely metastasizing neoplasm , which is defined as the ones which have a documented ability to metastasize but seldom do . as a group ,
they have < 2% chances of distant spread which can not be predicted on the basis of histomorphology .
the more common sites of distant metastasis are lungs and lymph nodes although distant seeding of kidneys and brain have been documented .
it has been well documented in adult stss for staging , response evaluation , and recurrence setting . in a meta - analysis ,
the sensitivity and specificity of fdg pet - ct in identifying primary as well as metastatic disease in stss were found to be 92% and 73% .
chen et al . reported a case of ifs with local recurrence demonstrated by fdg pet - ct .
the lesion was found to be low - grade fdg avid ( suvmax < 2.5 ) .
our case of this rare pediatric neoplasm originating from an extremity uniquely presented with distant soft - tissue metastasis within 1 year of receiving nact and surgery .
the fdg avidity of metastatic lesions was unusually high unlike reported in the literature so far .
our findings revealed fdg pet - ct as a potentially useful tool in detection of metastatic disease recurrence in ifs cases .
furthermore , metabolic parameters such as suvmax can be evaluated as prognostic tools to assess the tumor aggressiveness .
 infantile fibrosarcoma ( ifs ) is a rare soft - tissue sarcoma originating from extremities and occasionally from axial soft tissue . 
 the prognosis is good with favorable long - term survival . 
 it is rarely metastasizing tumor , the chances being lesser with ifs originating from extremities . 
 use of neoadjuvant chemotherapy ( nact ) as a treatment regime further reduces the chances of local relapse and distant metastasis . 
 the organs commonly affected in metastatic ifs are lungs and lymph nodes . 
 we report an unusual case of an ifs originating from extremity , which received nact , yet presented with an early metastatic disease involving soft tissues and sparing lungs and lymph nodes , as demonstrated on fluorodeoxyglucose positron emission tomography - computed tomography . 
INTRODUCTION
CASE REPORT
DISCUSSION
CONCLUSION
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