Abstract

BACKGROUND
Gastrointestinal stromal tumors (GISTs) are the most common mesenchymal tumors in the gastrointestinal tract. Expression of KIT protein (CD117) is an important diagnostic criterion of GIST. However, about 5% of GISTs are CD117 negative. Discovered on GIST 1 (DOG1) was introduced recently as a promising marker for GIST. We tested this new antibody in 105 GISTs tissue specimens, including 6 cases of metastatic GISTs, to determine the usefulness of DOG1 expression in the diagnosis of GISTs.
METHODS
We performed immunohistochemical (IHC) staining for DOG1 and CD117 on tissue microarrays that included 70 gastric GISTs, 29 small intestinal GISTs, 6 metastatic GISTs, 14 gastric leiomyomas and 16 gastric schwannomas.
RESULTS
DOG1 was positive in 98.1% (103/105) of GISTs and CD117 was positive in 97.1% (102/105) of GISTs. Only 1 case was negative for both markers. Two (66.7%) out of 3 GISTs tested CD117 negative were tested DOG1 positive. All leiomyomas and schwannomas were negative for both DOG1 and CD117.
CONCLUSIONS
DOG1 was highly expressed in GIST including CD117 negative cases. Adding DOG1 testing to the IHC panel for diagnosing GIST will help to identify GIST patients who are CD117 negative but may otherwise benefit from targeted therapy.

• Keywords: Gastrointestinal stromal tumors;DOG1;CD117;Immunohistochemistry