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adenocarcinoma is the most common malignant gastric tumor , while gastrointestinal stromal tumors ( gists ) are relatively rare . from all gastrointestinal locations ,
gists occur most frequently in the stomach ( 60 - 70% ) . however , a combination of an adenocarcinoma and a gist is a very rare finding and an actual collision of these tumors even more so .
this case report is , to our best knowledge , the second report in literature .
laboratory data demonstrated an esr of 15 mm / h ( normal 1 - 7 mm / h ) , a hemoglobin level of 6.5 mmol / l ( normal 8.5 - 11.0 mmol / l ) , thrombocytes 341  10 ( normal 150 - 400  10 ) , leukocytes 8.9  10 ( normal 4.0 - 10.0  10 ) .
endosonography showed an irregular course of the gastric wall where it was adjacent to the liver , not excluding possible invasive growth into the liver and thus suggesting the possibility of a t4 carcinoma .
sonography of the neck region and the abdomen showed no lymph node involvement or signs of metastasis to other organs .
primary surgery consisting of a total gastrectomy with roux - en - y esophagojejunostomy was performed . except from a postoperative septic period as a result of a spondylodiscitis , which was successfully treated with antibiotics ,
two and a half years after the total gastrectomy the patient developed pleural effusion due to adenocarcinoma metastases and died shortly thereafter . the resected specimen consisted of a totally resected stomach with en bloc part of the distal oesophagus . alongside the lesser curvature
on cut section the tumor invaded through the muscularis propria into the fat of the omentum minus . microscopically the tumor consisted of both a conventional adenocarcinoma and tumor nodules composed of cells with another phenotype .
most of the adenocarcinoma was found in the submucosa , but focally the adenocarcinoma invaded all layers of the gastric wall into the outer serosal surface or perigastric fat .
this tumor was composed of a combination of intestinal , gland - forming growth and a diffuse , poorly adhesive , often signet - ring morphology .
it consisted of nodules up to 6 mm composed of spindle cells with little cytonuclear polymorphism and with no significant amount of mitosis ( < 5/50 hpf ) ( fig .
1b ) and cd34 , while other stromal cell markers like s100 , smooth muscle actin and desmin were not expressed .
laboratory data demonstrated an esr of 15 mm / h ( normal 1 - 7 mm / h ) , a hemoglobin level of 6.5 mmol / l ( normal 8.5 - 11.0 mmol / l ) , thrombocytes 341  10 ( normal 150 - 400  10 ) , leukocytes 8.9  10 ( normal 4.0 - 10.0  10 ) .
endosonography showed an irregular course of the gastric wall where it was adjacent to the liver , not excluding possible invasive growth into the liver and thus suggesting the possibility of a t4 carcinoma .
sonography of the neck region and the abdomen showed no lymph node involvement or signs of metastasis to other organs .
primary surgery consisting of a total gastrectomy with roux - en - y esophagojejunostomy was performed . except from a postoperative septic period as a result of a spondylodiscitis , which was successfully treated with antibiotics ,
two and a half years after the total gastrectomy the patient developed pleural effusion due to adenocarcinoma metastases and died shortly thereafter .
the resected specimen consisted of a totally resected stomach with en bloc part of the distal oesophagus . alongside the lesser curvature
on cut section the tumor invaded through the muscularis propria into the fat of the omentum minus . microscopically the tumor consisted of both a conventional adenocarcinoma and tumor nodules composed of cells with another phenotype .
most of the adenocarcinoma was found in the submucosa , but focally the adenocarcinoma invaded all layers of the gastric wall into the outer serosal surface or perigastric fat .
this tumor was composed of a combination of intestinal , gland - forming growth and a diffuse , poorly adhesive , often signet - ring morphology .
it consisted of nodules up to 6 mm composed of spindle cells with little cytonuclear polymorphism and with no significant amount of mitosis ( < 5/50 hpf ) ( fig .
1b ) and cd34 , while other stromal cell markers like s100 , smooth muscle actin and desmin were not expressed .
these tumors are the most common mesenchymal tumors in the digestive tract and are thought to originate either from the stem cells that differentiate towards interstitial cells of cajal , or directly from interstitial cells of cajal [ 3 , 4 ] .
small gists are often detected incidentally during surgery for other reasons , or are detected during gastroscopy . in general , gists can be differentiated from other tumors made up from spindle cells and/or epitheloid cells by expressing cd117 ( c - kit ) and cd34 in 50 - 80% of cases [ 3 , 4 ] .
the kit gene codes for c - kit protein which activates a tyrosine kinase after binding with a stem cell factor .
90% of gists have a mutation in the kit oncogene , but 10% miss this mutation .
these sometimes cd117-negative tumors often have a mutation in the platelet - derived growth factor receptor a ( pdgfra ) . nowadays , the prognosis and biological behaviour of gist depends on a combination of two criteria : the size of the tumor and the mitotic index .
approximately 70 - 85% of patients have a complete resection , but overall five - year survival is only 50% , because of the tendency of the gist to metastasize or to recur . since 2002 a new therapy , imatinib mesylate , is developed to treat this kind of malignancies when metastasized or irresectable .
this is a tyrosine kinase inhibitor and demonstrates dramatic effects in the majority of patients .
possibly the kind of kit gene mutation has an effect on the development of resistance and the tumor response on imatinib .
the development of gastric collision tumors is very rare . in the english literature we found one case report describing the occurrence of an adenocarcinoma mixed with a gist .
several cases describing various other combinations of tumor have been reported [ 7 , 9 , 10 , 11 ] .
they considered whether or not such an association was incidental or whether the two lesions were connected by a causal relationship .
some articles suggest that gene mutations or a single carcinogenic agent might interact with two neighboring tissues , inducing the development of tumors of different histiotypes in the same organ , but no evidence of this last hypothesis has yet been found [ 8 , 10 ] . both tumors have different precursor cells and molecular make - up , and if there were a single carcinogen , these types of tumor would probably be diagnosed more often . in this case
the diagnosis of gist was made based on the tumor phenotype in combination with immunoreactivity to cd117 and cd34 .
the gist was presumed to be benign due to the low mitotic count , size and to a lesser extent the low degree of cellularity and cellular polymorphism .
although multicentricity is often considered a sign of malignancy , in this case , only very small nodules with no histological signs of malignant clinical behavior were present .
therefore it was expected that in this case the prognosis would most probably be determined by the adenocarcinoma component as this tumor penetrated the entire gastric wall into the serosa , had invaded blood vessels and showed lymph node metastasis .
we present a patient suffering from a collision tumor consisting of an adenocarcinoma originating from the gastric mucosa and a gist that was presumed to behave in a benign fashion .
as shown by the adenocarcinoma metastasis in the pleural effusion and death two and a half years after surgery , the patient 's prognosis was determined by the adenocarcinoma component .
. however , an actual collision of both an epithelial adenocarcinoma and a gist is exceedingly rare and as far as we know now , both with different and unknown etiology .
a collision tumor of the stomach is a rare event . 
 we report the case of a collision tumor of the stomach consisting of an adenocarcinoma and a gastrointestinal stromal tumor ( gist ) . 
 this is , to our knowledge , the second report in the literature of such a case . 
 a 71-year - old man with abdominal discomfort underwent an esophagogastroduodenoscopy which revealed a tumor of the oesophagogastric junction . 
 a total gastrectomy was performed . 
 histologic examination showed a mixed tumor consisting of a primary adenocarcinoma and multiple nodules of gist . 
 the adenocarcinoma showed both diffuse and intestinal growth , angio - invasion and metastasis to lymph nodes . 
 the gist tumor cells were strongly immunoreactive to cd117 and cd34 . based on mitotic index , size and cytonuclear details , the biological behavior of this gist tumor 
 was supposed to be benign . 
 this case reports the rare finding of a collision tumor consisting of an adenocarcinoma and a gist with an unknown etiology .