Differential Expression of Two Different DOG-1 Antibodies: Utility in Detecting Gastrointestinal Stromal Tumors

Abstract

Gastrointestinal stromal tumors (GIST) usually occur within the bowel wall, and most contain KIT - or PDGFRA - activating mutations. The routine diagnosis of GIST relies on C-kit immunohistochemical detection; however, up to 15% of GISTs are C-kit negative. Antibodies with increased sensitivity and specificity in the detection of C-kit–negative GIST cases could be of value because these cases could also benefit from imatinib mesylate therapy. We investigated two DOG-1 antibody clones, SP31 and K9, to determine which would be more useful in the diagnosis of GIST. Immunohistochemistry was performed on 40 GISTs, five adenoid cystic carcinomas, five mastocytomas, and five seminomas. Two DOG-1 antibody clones (SP31 and K9), two C-kit antibody clones (polyclonal C-kit and monoclonal C-kit), and monoclonal protein kinase C theta (PKCθ) antibody were analyzed. Both DOG-1 antibodies were found to have a high sensitivity and specificity in diagnoses of GIST. They were also both more sensitive and more specific than either C-kit. PKCθ showed a lower sensitivity but an equal specificity to both DOG-1 antibodies. This study demonstrates the usefulness of DOG-1 for diagnosing GIST, especially in C-kit negative cases. (The J Histotechnol 33(2):71–75, 2010)Submitted December 22, 2009; accepted with revisions May 12, 2010.