Glutamate receptor 2 (GRIA2) is a ligand-gated ion channel that uses L-glutamate for excitatory synaptic transmission expressed in the central nervous system.  A recent gene expression profiling study reported >100 fold GRIA2 induction in solitary fibrous tumors compared with control tissues.    Immunohistochemistry studies demonstrated GRIA2 positivity in the majority of solitary fibrous tumors (64-86%).  Its diagnostic performance yields 64% sensitivity, 92% specificity, with 41% and 97% positive and negative predictive value, respectively for the differential diagnosis of solitary fibrous tumors versus other mesenchymal soft tissue tumors.  GRIA2 may be a useful marker to identify STAT6-negative solitary fibrous tumors.