LOH 1p/19q typically occurred in tumors without TP53 mutations and were most frequent in oligodendrogliomas (69%), followed by oligoastrocytomas (45%), but were rare in fibrillary astrocytomas (7%) and absent in gemistocytic astrocytomas.
DNA sequencing, performed in 84% of cases, revealed that TP53 mutations were most frequent in gemistocytic astrocytomas (88%), followed by fibrillary astrocytomas (53%) and oligoastrocytomas (44%), but were infrequent (13%) in oligodendrogliomas.
In this study, gemistocytes and non-gemistocytic neoplastic cells were separated by laser-assisted microdissection from six gemistocytic astrocytomas carrying TP53 mutations.
These results indicate that p53 mutations are a genetic hallmark of gemistocytic astrocytomas, whilst PTEN mutations are absent in low-grade and rare in anaplastic gemistocytic astrocytomas.