Image Description
At higher power, the nuclei in a GIST are spindled, with blunt or rounded edges and dispersed chromatin with occasional small nucleoli. The background cytoplasm is eosinophilic and fibrillary. Rare lymphocytes are present throughout the tumor. Note the presence of prominent cytoplasmic vacuoles at either ends of the nuclei - generally considered to be a sign of smooth muscle differentiation in a GIST.