On immunohistochemistry, the tumor cells were immunoreactive for neuron-specific enolase (NSE), synaptophysin, chromogranin, CD56, Bcl-6, CD99, and peripherally for S100, but nonreactive for cytokeratin (CK), smooth muscle actin (SMA), and epithelial membrane antigen (EMA). This evidence concerns the gene CD99 and neoplasm.