BRAF alterations are frequent in cerebellar low-grade astrocytomas with diffuse growth pattern

Cristiane M. Ida, Sally R. Lambert, Fausto J. Rodriguez, Jesse S. Voss, Brooke E. Mc Cann, Amber R. Seys, Kevin C. Halling, V. Peter Collins, Caterina Giannini

Research output: Contribution to journalArticlepeer-review

31 Scopus citations


Cerebellar low-grade astrocytomas with a diffuse pattern of growth are uncommon, comprising World Health Organization (WHO) grade II diffuse astrocytomas (DA) and a minority of WHO grade I pilocytic astrocytomas (PA), so-called PA, "diffuse variant." Among 106 cerebellar low-grade astrocytomas (WHO grade I and II) operated on at the Mayo Clinic (1984-2010), we identified 19 such cases: 8 PA, "diffuse variant," 5 DA, and 6 that we were unable to classify further (low-grade astrocytomas, subtype indeterminate). We characterized these tumors using immunohistochemistry and currently available molecular markers (IDH1/2 mutations and BRAF mutation/fusion gene status) and investigated whether the markers could be used to aid the diagnostic process in combination with the clinical and pathologic features. KIAA1549-BRAF fusion was detected in 4 PA, "diffuse variant," 2 DA, and 2 low-grade astrocytomas, subtype indeterminate, indicating that these tumors were molecularly consistent with PA, the most common subtype of the series. A BRAF V600E mutation was detected in 1 PA, "diffuse variant" case; an IDH1 R132G mutation was found in 1 DA case. These results suggest that KIAA1549-BRAF fusion status and IDH1/2 and BRAF V600E mutational analyses may assist in the histologic classification of this diagnostically challenging group of tumors and result in a more accurate and objective combined molecular and histologic classification.

Original languageEnglish (US)
Pages (from-to)631-639
Number of pages9
JournalJournal of Neuropathology and Experimental Neurology
Issue number7
StatePublished - Jul 2012


  • BRAF
  • Cerebellar astrocytoma
  • Diffuse
  • IDH1
  • IDH2
  • Low grade
  • Pilocytic

ASJC Scopus subject areas

  • General Medicine


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