[Application of BRAF V600E mutation-specific immunohistochemistry in diagnosis of gastrointestinal stromal tumors].

OBJECTIVE: To evaluate the utility of BRAF V600E allele-specific antibody in the diagnosis of gastrointestinal stromal tumors (GISTs).

METHODS: BRAF V600E mutation-specific immunohistochemistry and BRAF sequencing were performed in 24 consecutive GISTs, including 14 cases of KIT or PDGFRA mutations and 10 cases of KIT/PDGFRA wild GISTs.

RESULTS: GISTs of 11 men and 13 women with a mean age 54 years(range 29-75 years) were included with tumors arising from stomach (16 cases), small bowel (7 cases), and peritoneal cavity (1 case). Strong and diffuse cytoplasmic BRAF staining was noted in 4 of 24 cases (17%), while 1 of 24 cases (4%) showed weak staining, and 19 of 24 cases (79%) had no staining. The four cases with strong BRAF immunostain were confirmed to have BRAF mutations, including 3 cases in the stomach and 1 case in the small intestine. All tumors showed spindle cell morphology. Only one case had progressive disease. No BRAF mutations were detected in cases with weak or negative BRAF immunostain.

CONCLUSION: BRAF V600E mutation-specific immunohistochemistry is a highly sensitive and specific marker for detecting BRAF-mutated GISTs.