Figure 1 shows comparative immunohistochemical investigations with hematoxylin & eosin (HE), glial fibrillary acidic protein (GFAP) and MIB-1 in the cases of grade II PXA and associated anaplastic PXA, and illustrative examples of histological assessment of BRAF V600E mutation (PXA-3) and CD34 immunoreactivity (PXA-1) are included on Additional file 2: Figure S1. The gene discussed is MIB1; the disease is pleomorphic xanthoastrocytoma.