1 – Pathology and Molecular Genetics of Common Brain Tumors

Publisher Summary This chapter provides an outline of the surgical pathology and the recognized genetic and molecular changes of common tumors of the nervous system in children and adults. The histological basis for classification and malignancy grading of the tumors and some common diagnostic problems are also addressed. Many brain tumors are morphologically heterogeneous, and classification of brain tumors is dependent on the recognition of areas with the characteristic histology for a particular tumor type. However, molecular data is more and more often being requested in addition to the histopathological findings. In many other areas of oncology, such as lymphoma, breast cancer, and sarcoma diagnosis, molecular data are the norm. The increasing number of evidence indicate that mutation at codon 132 of IDH1 (or rarely mutation of codon 172 of IDH2) combined with either TP53 mutation or total 1p/19q loss is a frequent and early change in the majority of oligodendroglial tumors, diffuse astrocytomas, anaplastic astrocytomas, and secondary glioblastomas, but not in primary glioblastomas. As new forms of molecular targeted therapy are introduced and found to be effective, the analysis of tumor specimens will have to be extended to provide clinically relevant data; medical professionals must be able to both provide this information and interpret the findings.