MDM2 and gastrointestinal stromal tumor: Immunohistochemistry showed absence of specific line of differentiation: the tumor cells stained positive for Vimentin but displayed no expression of epithelial markers (Cytokeratin MNF116, Cytokeratin 8/18, Cytokeratin 5, Cytokeratin 7, Cytokeratin 20, and EMA), melanocytic markers (S100 and SOX10), myogenic markers (SMA and Desmin), vascular markers (CD34 and ERG), lymphoid markers (CD45, CD3, CD20, CD5, and CD21), lipogenic markers (MDM2), or ‘gastrointestinal stromal tumor’ markers (CD117 and DOG1).