Diagnostic relevance of overexpressions of PKC-θ and DOG-1 and KIT/PDGFRA gene mutations in extragastrointestinal stromal tumors: a Korean six-centers study of 28 cases.

Abstract

The c-KIT, PKC-θ and DOG-1 antigens are the most sensitive and specific immunomarkers for confirming EGISTs. PKC-θ and PDGFRA immunostains are helpful markers for c-KIT-negative EGISTs. Survival analyses indicated that tumor size >10 cm, mitotic rate >10/50 HPFs, tumor necrosis, obvious nuclear atypia, and epithelioid or mixed cell type were significant predictors of survival. We found that the combination of these parameters helped to predict aggressive tumor behavior and may be useful for predicting the prognosis of EGISTs. The majority of gene mutations were identified in exon 11 of the KIT gene or exon 18 of the PDGFRA gene. The pattern of KIT and PDGFRA mutations in EGISTs was essentially similar to the one in GISTs. From the immunohistochemistry and molecular genetics perspective, EGISTs may be a special subtype of GISTs. Both immunohistochemical and molecular evaluation are useful for classifying tumors as EGISTs.