ABSTRACT
We present a case of an 83-year-old female patient with a collision tumour of an advanced Borrmann type 4 gastric cancer and a large gastric gastrointestinal stromal tumour (GIST). According to the deformity of the gastric wall caused by the GIST, type 4 cancer was difficult to identify by oesophagogastroduodenoscopy (OGD). The patient died of progressive gastric cancer related disease. While the mechanism of histogenesis of the simultaneous adenocarcinoma and GIST remains to be determined, the present case suggests that gastric adenocarcinoma has a more adverse effect on prognosis than does GIST. Additionally, this case suggests that thorough inspection of GIST patients is required at the OGD and at the pathology facility, in order to avoid overlooking the underlying cancer.