Prognosis-related histomorphological and immunohistochemical markers in central nervous system tumors of childhood and adolescence

Brain tumors account for approximately 20% of all childhood cancers, and are the leading cause of cancer morbidity and mortality among children. Although numerous demographic, clinical and therapeutic parameters have been identified over the past few years that have significant prognostic bearing for some pediatric brain tumors, predicting the clinical course and outcome among children with central nervous system tumors is still difficult. A survey of publications on prognosis-related histopathological and immunohistochemical features among pediatric brain tumors revealed 172 series, of which 91 presented statistically significant outcome-associated parameters as defined by a P value of less than 0.05. Most investigations revealing significant prognosis-related markers were performed on medulloblastomas (30 publications), ependymomas (25) and astrocytic tumors (18). In total, 16 cohorts consisted of more than 100 cases (5 on ependymomas, 3 each on medulloblastomas and astrocytic tumors). On the other hand, there were also 13 series with fewer than 20 cases (5 on medulloblastomas). Potentially prognostic histopathological markers vary among different entities and consist of assessment of necroses, mitoses, differentiation, vascular proliferation, and growth pattern, whereas immunohistochemical features include proliferation markers (Ki-67, MIB-1), expression of oncogenes/tumor suppressor genes and their proteins (TP53, c-erbB2), growth factor and hormonal receptors (VEGF, EGFR, HER2, HER4, ErbB-2), cell cycle genes (p27, p14ARF) and cell adhesion molecules, as well as factors potentially related to therapeutic resistance (DNA topoisomerase IIalpha, metallothionein, P-glycoprotein, tenascin). This review discusses the prognostic potential of histopathological and immunohistochemical markers that can be investigated by the practicing neuropathologist as part of the routine diagnostic workload, and scrutinizes their benefit for predicting therapy response and patient outcome among children with brain tumors.