CD34 and pleomorphic xanthoastrocytoma: Histologically, three cases (75%) were diagnosed as WHO grade II PXA and one case (25%) as WHO grade III anaplastic PXA; neoplastic cells exhibited an immunopositivity for GFAP in 4/4 cases and for synapthophysin in 1/4 cases; extravascular positivity for CD34 was observed in 3/4 cases.