Comparative study for immunohistochemical expression of DOG1 versus CD117 in diagnosis of gastrointestinal stromal tumors

Abstract

GISTs are the most common mesenchymal tumors of the alimentary tract. They occur at any site along the GIT, but they are more common in the stomach and the small bowel. Most (~95%) GISTs show positive immunoreactivity for C-KIT protein. However, recent studies have identified a small group (about 5%) of C-KIT negative GISTs with KIT or PDGFRA mutations, which may be sensitive to imatinib therapy. These cases require special attention for diagnosis. The novel gene DOG1 (discovered on GIST- 1), has emerged in recent years (2004) as a promising biomarker for GIST. It was originally discovered through expression profiling analysis as a gene that is highly expressed in GIST, and subsequent immunohistochemical studies have shown its use in the diagnosis of GIST. The aim of this study was to evaluate the immunohistochemical expression of DOG1 in GIST cases and compare it with C-KIT as regard sensitivity. The present study comprised 50 cases previously diagnosed as GIST, collected from the archival material at the pathology department of Ain Shams University Hospitals and Ain Shams Specialized Hospital. Summary - 176 - The age of cases in this study ranged from 28 to 73 years and the mean age was 53.24 10.159. The most frequent age group was (41- 60) representing (66%). The male: female ratio was 1.1:1. The size of the tumor in this study ranged from 2 cm to 40 cm. The most frequent size was >10 cm accounting for 54% of all cases. The most frequent site of GIST in the present study was the stomach (48%) followed by the small intestine (26%). Histopathological examination revealed that; the most common histological type in this study was spindle cell type (62%) followed by mixed (epithelioid and spindle) (32%) and then epithelioid morphology (6%). Regarding the mitotic activity, the mitotic figures of 44% of cases were 6-10 /50 HPF, in 40% of cases they were less than 5 /50 HPF and 16% of tumors had mitotic figures more than 10 /50 HPF. Most of the collected cases were high risk tumors (74%) followed by intermediate risk (18%) and then low risk tumors (8%). Concerning tumor necrosis, (40%) of the cases were positive for tumor necrosis in this study. Twenty percent of the cases had metastasis mainly to the lymph nodes followed by the liver. There was a highly significant statistical correlation between the site of tumor and the age of the patients. The age of patients with gastric tumors was higher than those with small intestinal tumors. The correlation between the site and size of the tumor was Summary - 177 - statistically significant. Most cases located in the stomach, small intestine and EGIST were ˃10 cm in size.