Limitations of the World Health Organization classification of childhood supratentorial astrocytic tumors

BACKGROUND. In the context of many implied but not rigorously stated histol ogic feature combinations, the World Health Organization (WHO) classificati on of astrocytic tumors specifies only the presence or absence of endotheli al proliferation, necrosis, and mitosis to distinguish astrocytoma, anaplas tic astrocytoma, and glioblastoma multiforme. METHODS. The authors examined the effects of these and other reliably recog nized histologic features on survival in the Childhood Brain Tumor Consorti um (CBTC) sample of 340 children with supratentorial astrocytic tumors. RESULTS. Overall, the WHO criteria distinguished only two prognostically di stinct classes of astrocytomas. When the specific combinations of the three features were unambiguously designated, three diagnostic categories result ed. These revised diagnostic categories are consistent with WHO guidelines and have significantly different survival distributions. However, neither t he original WHO diagnoses nor the revised categories adequately separated t hese tumors prognostically, because histologic features other than those sp ecified by WHO were significantly associated with improved or worsened surv ival. CONCLUSIONS. Classifications based on small numbers of specified histologic features may not be feasible because they inadequately separate childhood astrocytic tumors into prognostically homogeneous groups. Preferable classi fication techniques are those that simultaneously account for all reliably recognized histologic features. Cancer 2000;88:1477-83. (C) 2000 American C ancer Society.