BRAF mutation and anaplasia may be predictive factors of progression-free survival in adult pleomorphic xanthoastrocytoma.

Background: Pleomorphic xanthoastrocytoma (PXA) is a rare, low-grade glioma that frequently occurs in pediatric patients.

Objective: To analyze adult patients diagnosed with PXA and to search for pathological and molecular markers of diagnosis and prognosis.

Methods: We retrospectively included patients older than 16 years with PXA who were referred to our institution between October 2003 and September 2013. All pathological diagnoses were reviewed by a neuropathologist. Histological characteristics and immunostaining of GFAP, OLIG2, neurofilament, CD34, Ki67, p53, p16, and IDH1 R132H were analyzed. The following molecular alterations were analyzed: mutations of IDH1/2, BRAF and the histone H3.3 and the EGFR amplification. Clinical data, treatment modalities, and patient outcome were recorded.

Results: We identified 16 adult patients with reviewed PXA diagnosis. No IDH neither histone H3.3 mutations were found; BRAF V600E mutation was recorded in six patients. Ten patients presented with anaplastic features. BRAF mutations were associated with lower Ki67, OLIG2 expression, and lack of p16 expression. Median PFS and OS were 41.5 months (95% CI: 11.4-71.6) and 71.4 months (95% CI: 15.5-127.3), respectively. BRAF mutation tended to be associated with greater PFS (p = 0.051), whereas anaplastic features were associated with minimal PFS (p = 0.042).

Conclusion: PXA in adults PXA may present features distinct from pediatric PXA. Anaplastic features and BRAF mutation may potentially identify specific subgroups with distinct prognoses.