Distinct clinicopathological features in metanephric adenoma harboring BRAF mutation.

mutation recently has been reported in metanephric adenoma. We sought to determine the clinical and morphologic features of -mutated metanephric adenoma and to correlate mutation with BRAF V600E immunohistochemical staining results. A series of 48 metanephric adenomas and 15 epithelial-predominant nephroblastomas were analyzed for the occurrence of mutation ( V600E/V600E complex, V600D, V600K and V600R) using the BRAF RGQ PCR kit (Qiagen). Immunohistochemistry was performed using monoclonal mouse antibodies against p16 and VE1 (Spring Bioscience), recognizing the BRAF V600E mutant protein. Forty-one of 48 cases (85%) showed V600E mutation; none of the other variants was detected. Of 41 -mutated metanephric adenomas, 33 showed positive VE1 immunostaining (sensitivity 80%, specificity 100%); in all cases we detected p16 expression regardless of mutation status. All epithelial-predominant nephroblastomas were -wild-type and none expressed VE1. The following features were associated with V600E mutation: older patients (p=0.01), female predominance (p=0.005) and the presence of a predominantly acinar architecture (p=0.003). In summary, -mutated metanephric adenomas were associated with older age, female predominance, and the presence of a predominant acinar component. A subset (20%) of -mutated metanephric adenomas was not detected by VE1 immunostaining.