CD99 and meningioma: Histopathologically, HPCs show a staghorn pattern of spindle cells11 and immunohistochemical staining shows strong positivity with vimentin (100% of cases), CD99 (94% of cases), and CD34 (88% of cases) but only focal positivity with Epithelial Membrane Antigen( EMA) (33% of cases).12,13 Meningioma however is strongly positive for both vimentin and EMA.