Infant brain tumors: a neuropathologic population-based institutional reappraisal.

The factors that impact the long-term functional outcome for infants with brain tumor are unclear. The clinicopathologic features of all infant brain tumors occurring at our institution (1982-2005) were reexamined to explore the factors influencing prognosis. The details of the neuropathologic review are reported herein. Thirty-five cases were identified and included 7 astrocytomas (6 low grade and 1 glioblastoma), 6 atypical teratoid rhabdoid tumors, 5 choroid plexus papillomas, 4 ependymomas (3 anaplastic), 4 teratomas (3 immature), 2 supratentorial primitive neuroectodermal tumors, 2 gangliogliomas, 2 desmoplastic tumors of infancy, and 1 each of "medulloblastoma with extensive nodularity," adamantinomatous craniopharyngioma, and 1 "malignancy not otherwise specified." The original diagnosis was changed in 8 cases (23%), and atypical teratoid rhabdoid tumors was the most common revision (n = 5). Case 9 was unusual in that both the patient and her 2-year-old sister displayed INI-1 immunonegative posterior fossa tumors and extended survival. Tumor grade was altered in 6 cases (17%), the most significant instance being the downgrading from the World Health Organization grade IV to I (case 18: supratentorial primitive neuroectodermal tumors to desmoplastic tumors of infancy). As opposed to other reports in the literature, our cohort contained a substantially higher frequency of atypical teratoid rhabdoid tumors and a lower frequency of medulloblastoma. Changes in the histologic diagnosis/grade in a significant subset of cases most likely reflect the continual evolution of brain tumor classification schemes. INI-1 immunohistochemistry was instrumental in the pathologic assessment of select cases and raised the possibility that atypical teratoid rhabdoid tumors may be the most common infant brain malignancy.