Pediatric brain tumors: a histologic and genetic update on commonly encountered entities

As our understanding of pediatric brain neoplasia flourishes, so does the development of diagnostic, prognostic, and predictive biomarkers. The neuropathologist uniquely stands at the crossroads between pathology and molecular genetics, often overseeing the creation, development, implementation, delivery, and reporting of the newest bioassays. This review serves to highlight the key microscopic and genetic features of the most common pediatric brain tumors. For example, INI-1 immunohistochemistry has assisted in identifying several previously unrecognized cases of rhabdoid cell-poor atypical teratoid rhabdoid tumor (ATRT). The latest discovery involving the tandem duplication and fusion BRAF-KIAA1549 on chromosome 7q34 in pilocytic astrocytoma has drawn attention to the MAPK-ERK pathway and its potential chemotherapeutic manipulation. The newly identified IDH1 mutation, which appears characteristic of "secondary astrocytomas," has yet to be studied in the pediatric population, but some researchers have extolled concomitant BRAF-KIAA1549/IDH1 analysis in the neuropathologic workup of many astrocytomas. Through these and other advances, our understanding of pediatric brain tumors will continue to expand exponentially, and as such will set the stage for truly effectual future treatments.