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Paper text:
adenocarcinoma is the most common type of malignant gastric neoplasm ( 95% ) but gastrointestinal stromal tumors ( gists ) have relatively appeared rare ( 1% ) [ 1 - 4 ] .
gists and adenocarcinoma are distinct malignancies originating from different cell layers and the simultaneous development of a gist and gastric adenocarcinoma is relatively rare [ 5 - 10 ] . here
we present a very rare combination of synchronous prepyloric gastric adenocarcinoma and a gist of fundic body region .
sixty four - year - old female has admitted to our hospital complaining of dyspeptic symptoms , during the last 2 months .
chest x - ray and abdominal ct - scan have not shown any signs of metastasis .
subsequently the patient has undergone an elective subtotal gastrectomy and billroth - ii gastrojejunal anastomosis during the operation .there was a second nodule has palpated in the fundic body region at the greater curvature which has separately resected .
pathology examination has shown a polypoid and infiltrative circumferential mass that has measured 642 cm in antropyloric region on macroscopic examination . in gross examination of specimen
the histopathologic examination has revealed a signet ring type poorly differentiated adenocarcinoma of stomach , that has been infiltrating the wall and reaching the subserosa .
the separate nodule of fundic body region of stomach was a well circumscribed tan elastic tumoral mass measuring 1 cm in diameter . in microscopic examination
it was a spindle cells neoplasm located in muscularis propria extending up to serosa composed of intersecting fascicles of spindle cells with abundant eosinophilic fibrillar cytoplasm and minor degree of nuclear pleomorphism ( figure 2 ) . in immunohistochemical study focal positivity for desmin ( figure 3 ) and diffuse strong positivity for cd117 ( figure 4 ) have detected which has confirmed the diagnosis of gastrointestinal stromal tumor .
the patient has received imatinibas adjuvant therapy for the gist , according to the international guidelines for gists risk stratification .
four month later on her follow up visit she has shown clinically and radiographically disease free .
the collision of adenocarcinoma and gist in the stomach is extremely rare and to the best of our knowledge only few cases have been reported in the english literature [ 5 - 10 ] . in the cases
the synchronous tumors have located in different parts of the stomach , in our case there was prepyloric gastric signet cell adenocarcinoma and a proximal gastric gist .
gists are typically sessile big soft tumors and could develop necrosis or ulceration of overlying mucosa .
however when the gist is sub mucosal or subserosal the gastric mucosa might not be invaded and endoscopic assessment could be normal . in our case preoperative diagnosis was adenocarcinoma and during laparotomy we have incidentally found a small nodule in proximal part of stomach and the histopathological and immunohistochemical examination of the specimen have revealed the diagnosis of gist .
this designates a heterogeneous group of mesenchymal malignancies that consist of spindle or epithelioid cells with varying degrees of differentiation .
these tumors had an annual incidence of approximately 10 - 15 cases per 1 million people ; however gists are the most common mesenchymal tumors of the gastrointestinal tract accounting for 0.1 to 3% of all gi tumors [ 12 , 13 ] .
these tumors are thought to originate either from the stem cells that differentiate towards interstitial cells of cajal or directly from interstitial cells of cajal [ 14 , 15 ] . in general gists
could distinguish from other spindle or epithelioid cell tumors by expressing cd117and cd 34 in 50 - 80% of cases [ 14 , 15 ] .
ninety percent of gists have a mutation in the kit oncogene but 10% miss this mutation .
approximately 70 - 85 % of patients have a complete resection but overall five - year survival is only 50% .
since 2002 a novel therapy , imatinib mesylate , has introduced to treat this kind of malignancies .
this is a tyrosine kinase inhibitor and has demonstrated with great dramatic effects in majority of patients [ 16 , 17 ] .
they have considered whether such an association was incidental coexistence , or the two lesions have connected by a connecting relationship .
some articles suggest that gene mutations or a single carcinogenic agent might interact with two neighboring tissues inducing tumors development of different histotypes in the same organ . but no evidence of this last hypothesis has yet been found [ 10 , 21,22 ] .
both tumors have different precursor cells and molecular make up and if there were a single carcinogen , these types of tumor would probably diagnose .
more often simple coincidence have also known as the case especially in geographical regions with high incidence rate of gastric cancer such as japan .
although helicobacter pylori infection has been implicated in gastric cancer development , there is no evidence of such association in gist .
n - methyl - n nitro - nnitrosogunidine has inducedgastric adenocarcinoma development of following oral administration in rats   and when it has combined with agents such as aspirin or stress , leiomyosarcomashas developed in combination with epithelial tumors .
other articles have reported induction of gastric adenocarcinoma after injection of 9 , 10-dimethyl-1 , 2-benzanthrancene ( dmba ) where management with dmba and cellophane plate could cause mainly the induction of gastric sarcomas . in collision tumors
the adenocarcinoma has been determined to have a greater unfavorable effect on prognosis than the gist , even if the gist has belonged to the high - risk group .
simultaneous a collision tumor of stomach consisting of adenocarcinoma and gastrointestinal stromal tumor ( gist ) is very rare based on our knowledge . 
 this coexistence has rarely been reported in literatures.we report a case of 64-year - old woman who has diagnosed with prepyloric poorly - differentiated diffuse signet - ring cell type adenocarcinoma and has undergone an elective d2 total gastrectomy . during operation 
 another mass in fundic body region has found.the pathologic examination of the mass has shown gist . 
 immunohistochemical staining for cd117 and desmin was positive whilst that for s100 was negative.this case reports the simultaneous two tumors development of different histotypes and natures in the same organ .