Mixed pleomorphic xanthoastrocytoma and ganglioglioma with existence of BRAF V600E mutation

Abstract

Objective To investigate the clinicopathological and molecular genetic features of one case of mixed pleomorphic xanthoastrocytoma (PXA) and ganglioglioma (GG) with BRAF V600E mutation.  Methods and Results A 14-year-old boy mainly presented paroxymal loss of consciousness and tic of limbs for 6 years. Head MRI displayed circular abnormal signal on the hippocampus of left temporal lobe, considering space-occupying lesion. The patient underwent operation, and the lesion was totally removed. Pink gyri in deep temporal lobe could be seen during the operation. The tumor tissue was red grey, tough, nonencapsulated, with calcification, cystic degeneration, rich blood supply and clear boundary. Morphology showed the tumor grew diffusely and was heterogeneous: some areas showed the structure of GG and others showed the structure of PXA. Immunohistochemical staining and special staining showed in the region of GG, the tumor was scatteredly positive for glial fibrillary acidic protein (GFAP) and neurofilament protein (NF), gangliocyte-like cells were positive for microtubule associated protein-2 (MAP-2) and neuronal nuclei (NeuN), Ki-67 labeling index was 2%; in the region of PXA, spindle tumor cells were scatteredly positive for GFAP and NF, xanthomatoid cells were positive for CD163 and CD68, Ki-67 labeling index was 3%-5%, reticular fibers were abundant. Molecular detection showed that BRAF V600E mutation existed in both parts of the tumor. The patient was not treated by postoperative radiotherapy or chemotherapy. He took antiepileptic drugs (AEDs) orally [sodium valproate 1.20 g (twice a day) and levetiracetam 0.50 g (twice a day)] for one year, and the symptoms were greatly improved. He had no evidence of tumor recurrence in the 18-month follow-up period.  Conclusions Combined PXA and GG is a rare tumor of the central nervous system (CNS). The tumor showed different morphological features of PXA and GG, but with the same BRAF V600E mutation molecular characteristics. This case may support the study on morphology, histological origin and molecular genetics for PXA and GG.

DOI: 10.3969/j.issn.1672-6731.2017.03.008