Histopathological Features of Gastrointestinal Stromal Tumors and the Contribution of DOG1 Expression to the Diagnosis

Background: Gastrointestinal stromal tumors (GIST) have KIT or platelet-derived growth factor receptor a (PDGFR alpha) mutations affecting receptor tyrosine kinase activity and do not benefit from classic treatment regimens. Aims: The aim of this study was to review the algorithm that may be followed for the diagnosis and differential diagnosis in GISTs by investigating the histomorphological parameters and expression characteristics of classical immunohistochemical antibodies used in routine tests in addition to DOG1 expression. Study Design: Diagnostic accuracy study. Methods: We reevaluated the histological and immunohistochemical parameters of 37 GISTs. The standard immunohistochemical diagnosis and differential diagnosis panel antibodies (CD117, PDGFR alpha, CD34, vimentin, desmin, SMA, S-100, and Ki67) were studied on the tumor sections. We also used the popular marker DOG1 antibody with accepted sensitivity for GISTs in recent years and the PDGFR alpha immune marker for which the benefit in routine practice is discussed. Results: Classification according to progressive disease risk groups of the 37 cases revealed that 54% were in the high risk, 19% in the moderate risk, 16% in the low risk, 8% in the very low risk and 8% in the no risk group. Cytological atypia, necrosis, mucosal invasion and the Ki67 index were found to be related to the progressive disease risk groups of the tumors (p<0.05). Positive immunoreaction was observed with CD117 and PDGFR alpha in all GISTs in the study (100%). Positivity with the DOG1 antibody was found in 33 (89%) cases. CD34 was positive in 62% (23) of the cases. Conclusion: The CD117 antibody still plays a key role in GIST diagnosis. However, the use of DOG1 and PDGFR alpha antibodies combined with CD117 as sensitive markers can be beneficial.