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intraabdominal desmoplastic small round cell tumors ( dsrct ) are rare , but aggressive mesenchymal malignancies of uncertain origin .
it usually presents with symptoms of abdominal pain , weight loss , nausea , vomiting , and a palpable abdominal mass .
findings at laparotomy frequently include peritoneal dissemination of uncertain origin , ascites , and occasionally visceral implantations forming a mass .
since primary gastrointestinal ( gi ) malignancies are rare in children , the mass - forming dsrct mimicking a gi tract tumor is difficult to diagnose before a laparotomy .
here we report a case of dsrct involving the stomach that was initially misdiagnosed as a gastric cancer .
laboratory tests revealed hemoglobin of 7.0 g / dl and no other abnormal findings . on gastroscopy ,
a 7-cm mass was noted at the esophago - gastric junction and posterior wall of the cardia .
the overlying mucosa and the bridging folds appeared normal , thus suggesting a submucosal tumor ( fig .
1 ) . abdominal computed tomography ( ct ) showed a large gastric mass with multiple enlarged retropancreatic and aortocaval lymph nodes ( fig .
2 ) . positron emission tomography ( pet ) showed multiple uptake suggesting metastases to the left supraclavicular , right pleural , pelvic and retroperitoneal lymph nodes ( fig .
based on the findings of malignant mass on gastroscopy and pathological examination , metastatic lesions on ct and pet , we diagnosed as the stage iv gastric cancer .
evaluation after the chemotherapy showed a slightly regressed gastric mass ; however , the retroperitoneal metastases progressed .
on laparotomy , a huge mass from the lesser curvature of the stomach invading the gastrohepatic ligament was noted along with numerous peritoneal implantations .
palliative proximal gastrectomy with esophago - gastric anastomosis was performed , and the final pathological examination revealed transmural involvement of dsrct ( fig .
the post - operative chemotherapeutic regimen was changed to ccg 7881b : cyclophosphamide , doxorubicin , and vincristine .
the patient underwent 8 cycles of ccg 7881b , but the residual disease showed no changes .
intraabdominal dsrct has rarely been reported in adolescents and young adult males , and few long - term survivors have been described and the survival prognosis following the diagnosis is an average of 23 months .
due to the highly aggressive nature and diffuse spread of the dsrct , systemic chemotherapy has been used as the initial treatment along with debulking surgery .
lal et al .   achieved an over 90% reduction of the tumor bulk in 71% of their patients and demonstrated a significant survival benefit , thus suggesting the benefit of aggressive surgical resection .
by contrast , livaditi et al .   reported that even radical surgical efforts were palliative with a dismal outcome despite all therapeutic modalities .
it was impossible in the case reported here to achieve a large volume reduction at surgery because of the massive retroperitoneal involvement .
whether it is worth sacrificing major organs such as the liver and pancreas for cytoreductive surgery in patients with dsrct is debatable .
primary gastric cancer , although rare , has been reported sporadically in children and the reported incidence is about 0.1% . however , dsrct of the stomach is extremely rare ; only one case has been previously reported in children .
the rarity of this condition along with the inconspicuous pathology led us to misdiagnose as stage iv gastric cancer before surgery .
we suggest that , when poorly differentiated malignancies of the stomach are being considered , dsrct should be in the differential diagnosis , especially among adolescent and young adult males . moreover ,
since dsrct can form a mass along the whole gi tract , thus mimicking a primary gi tract tumor , dsrct should be included in the differential diagnosis of primary gi tract tumors in children .
dsrct typically display clusters or nests of small round cells lying in a hypocellular , desmoplastic , collagenous stroma and this is a helpful diagnostic feature . in immunohistochemical staining
, the dsrct is usually positive for desmin ( dot - like expression ) and cytokeratin .
the case reported here satisfies the typical pathological and immunohistochemical staining profiles and we could make the diagnosis of dsrct , which was impossible before laparotomy .
the translocation fuses two specific genes : the ewing sarcoma gene ( found in ewing 's sarcoma ) and the wilms tumor 1 gene ( found in wilms ' tumor ) , and the resultant chimera protein is thought to act as a transcriptional regulator .
this transcriptional factor is known to regulate the expression of specific target genes , and the dysregulated expression of the target genes is related to the invasiveness of the dsrct .
recently , connective tissue growth factor ( ccn2 ) that is highly expressed in dsrct , has been found to regulate the tumor cell growth , matrigenesis , and angiogenesis of this tumor .
as conventional multimodal treatments fail to improve survival , future treatment should include specific targeted treatment focusing on these cellular regulatory mechanisms . "
initially responsive but soon refractory to the treatment and rapidly progressive " depicts the clinical behavior of the dsrct .
the case reported here showed an initial treatment - response of the gastric mass after the neoadjuvant chemotherapy ; however , the residual tumors remained nearly unchanged postoperatively after adjuvant chemotherapy with ccg 7881b .
the tumors are likely now in a refractory phase and will soon show rapid disease progression , eventually leading to the death of this patient . in summary ,
although post - operative chemotherapy was provided and the patient is now alive with residual disease , the prognosis is dismal .
intra - abdominal desmoplastic small round cell tumor ( dsrct ) is a highly malignant tumor of uncertain histogenesis . here 
 we report a case of dsrct involving the stomach , initially misdiagnosed as gastric cancer . a 12-year - old boy presented with upper abdominal pain developed 1 month prior . 
 on gastroscopy , a 7-cm mass was noted involving the esophago - gastric junction to the fundus , and positron emission tomography showed multiple hot uptakes suggesting distant metastasis . 
 gastroscopic biopsy showed poorly differentiated malignant cells . 
 we diagnosed as stage iv gastric cancer and treated with 6 cycles of chemotherapy . 
 laparotomy revealed a huge gastric mass along with peritoneal disseminations . 
 palliative proximal gastrectomy was performed . 
 pathological examination revealed transmural involvement of dsrct , and t(11;22)(p12;q12 ) was demonstrated on fluorescence in situ hybridization test . 
 the chemotherapeutic regimen was changed and the patient underwent 8 additional cycles of post - operative chemotherapy . 
 the patient is now alive and the residual tumor shows no significant changes after chemotherapy .