Background: Gastrointestinal Stromal Tumor (GIST), the most common gastrointestinal mesenchymal malignancy, requires immunohistochemistry (IHC) for pathological diagnosis and can be treated by targeted therapy or personalized medicine, which produce considerably fewer side-effects than conventional chemotherapy. The panel of antibodies used in different categories of hospitals and medical centers may vary, and the epidemiology of the tumor seems to be different in eastern and western patients. The present study aims to reorder suitable panels for tertiary care centers in terms of their efficacy as proven by research evidence.

Objective: To study the epidemiology and effectiveness of immunohistochemistry investigation of CD34, CD117, DOG-1 and SMA in GIST in Rajavithi Hospital (RJVH) from 2012 to 2017.

Materials and Methods: Data were retrospectively collected from all cases which had been pathologically diagnosed as GIST in the RJVH database from 2012 to 2017. Epidemiological information and effectiveness of immunohistochemistry investigation of CD34, CD117, DOG-1 and SMA were recorded.

Results: The study data consisted of 119 records. All subjects were of Thai nationality, most were female (52.9%), and their ages ranged from 27 to 84 years old, with an average of 59.35 years old. Patient expense per day varied from 3,087.5 to 130,100.0 THB (Thai Baht) and was 9,388.4 THB on average. The turnaround time (TAT) of IHC in 2, 3, 4 and 5 days was in 4, 108, 6 and 1 cases respectively, with most reported within 3 days. The most common organ involvements were stomach (41%), duodenum (8.5%) and rectum (8.5%), and the most prevalent secondary site was the liver (6.9%). The results of expression of the panel of IHC were recorded, and extragastrointestinal GIST was found 28.1% of cases.

Conclusion: Epidemiologically, there were some differences in age and sex of patients in the present study compared with those of western papers, but these data were similar to those of other eastern ones. The common primary and secondary sites, as well as the order of positive IHC expressions, were similar to those in the literature. With regard to efficacy, standard guidelines for largescale hospitals should include DOG-1 in the first panel because of its advantages in terms of time, expense and diagnostic confidence.

Keywords: Epidemiology, Worthiness, GIST, Immunohistochemistry, IHC, CD34, CD117, DOG-1, SMA