Abstract

BACKGROUND
Gastrointestinal stromal tumors (GIST) are the most common mesenchymal tumors in the gastrointestinal tract. Recently, many methods for the diagnosis of GIST have been developed including molecular diagnosis.
METHODS
We selected 90 cases of GIST that had presented at Kyungpook National University Hospital between 1998 and 2007. Tissue microarrays were made using core areas of tumor tissues. Immunohistochemical staining for c-kit, protein kinase C-theta, and platelet-derived growth factor receptor alpha (PDGFRA) was done. Direct sequencing of hot spot exonal areas for c-kit and PDGFRA were done using extracted DNAs of all 90 paraffin block tissues.
RESULTS
Among the 90 cases, 83.3% (75/90) were c-kit positive, 16.6% (15/90) were c-kit negative, 93.3% (84/90) were PDGFRA positive, and 6.6% (6/90) cases were PDGFRA negative. Fifteen cases of c-kit negative GIST included 1 case of PDGFRA negative and 5 cases of PDGFRA negative GIST were ckit positive. The one case in which both c-kit and PDGFRA were negative, showed a c-kit mutation in exon 11.
CONCLUSIONS
Combined immunohistochemical staining of c-kit, discovered on GIST 1 (DOG1) and PDGFRA is helpful for the diagnosis of GIST. When all staining tests are negative for immunoreactivity, c-kit mutation analysis for exon 11, 9 should be done. Genotyping of kit and PDGFRA do not need to be examined initially, if it is only for the diagnosis of GIST.

• Keywords: Gastrointestinal stromal tumors;c-kit;Receptors, platelet-derived growth factor alpha (PDGFRA);Mutation;Sequence analysis