Oligodendroglioma: An appraisal of recent data pertaining to diagnosis andtreatment

OBJECTIVE: This article reviews and summarizes recent data on the diagnosis , prognosis, and treatment of oligodendroglial tumors. METHODS: Histological criteria for optimized diagnosis and grading of oligo dendroglial tumors are described and discussed. The therapeutic approaches are analyzed in light of the results of recent series. RESULTS: Oligodendroglial tumors may be more common than is generally thoug ht. Perinuclear halo and "chicken-wire" pattern, although considered classi c histological features of oligodendrogliomas, are unreliable as sole crite ria for diagnosis. Nuclear regularity and roundness and an eccentric rim of eosinophilic cytoplasm lacking obvious cell processes are more constant fe atures. Grading should be accomplished using a composite of radiological an d histopathological relevant features. The allelic loss of chromosome arms 1p and 19q might be a marker for both chemosensitivity and longer survival after chemotherapy. Oligodendrogliomas are notably chemosensitive when comp ared with other gliomas. For aggressive lesions, chemotherapy should be use d upfront, after surgery. CONCLUSION: Oligodendrogliomas are underdiagnosed. One unfortunate implicat ion is that a large number of patients may be receiving suboptimal care. A simplification in grading of oligodendroglioma to two grades would reduce t he confusion surrounding the classification and better define prognosis and response to treatment modalities. A better definition of the so-called mix ed tumor should also allow a better classification of these lesions in an i ntermediate prognostic class between astrocytic and oligodendroglial lesion s. Loss of 1p and 19q could be used as a cytogenetic marker in assisting gr ading. New concepts emerging in the recent literature should help optimize the diagnosis of these lesions and reduce interobserver variability.