PTPRR and pleomorphic xanthoastrocytoma: Affymetrix gene microarray (HTA-2) expression analysis was additionally used to study 15 of the above AB-like tumors, one MN1-rearranaged tumor recurrence (C10r), the four PTPR, six histologically classic pleomorphic xanthoastrocytomas (PXA), four fetal brain samples (28–30 pcw) and 14 normal pediatric and adult brain samples.