Histologic classification and prevalence of tumors of the central nervous system in infants. Study of 100 excision samples

In order to assess the epidemiological and histological distributions of brain tumors in infants under 2 years of age, 100 cases collected in the Neurosurgery Department of Hôpital Necker-Enfants Malades in Paris during an 11 year period, were reviewed. Histopathological diagnoses were analyzed with special reference to age at the time of diagnosis, sex, topography and grading. Brain tumors were classified into 2 groups: under one year of age, and between 1 and 2 years of age. Certain neoplasms were reclassified after review of the slides. The male-to-female ratio was 1.09:1 for the first group, and 1.25:1 for the second one. In the group of tumors diagnosed under 1 year of age, 60% were supratentorial, and 40% were infratentorial. The percentages reversed after 1 year of age in favor of those of the posterior fossa. The histopathological distribution of these tumors was assessed in the two groups according to Rorke's classification. The three most common histological types were astrocytoma (27% under 1 year versus 36% after 1 year), ependymoma (25% versus 16%) and medulloblastoma (14% in each group). There was a significantly higher prevalence of some types of tumors in the first year of life as compared with those diagnosed after one year.: ependymomas (25% versus 16%), primitive neuroectodermal tumors (PNET) other than medulloblastomas (9% versus 3.5%), choroid plexus tumors (9% versus 17%), and teratomas (5% versus 1.7%). Craniopharyngiomas (2%) and non-tumoral lesions (vascular malformations) (7%) had similar distributions in both groups. There was a preponderance of malignant tumors in the first year of life. Our study demonstrates that brain tumors diagnosed during the first year of life have characteristic and specific features in terms of topography, histopathological distribution and grading.