Neuro-oncology has in the past decade undergone tremendous developments, so much so that it is now a scientific field of vast proportions. Molecular and genetic biology, on the one hand, and the improvements in imaging techniques, therapies, and general management, on the other, have been highly instrumental in effecting this progress. Despite all recent developments, descriptive pathology, however, with its many bio logical correlates - foremost among them immunohistochemistry - and, therefore, histological diagnosis and prognostic assessment continue to be the reference points for judging all new achievements in neuro-oncology. Years of experience of patients with brain tumors and collaboration with neurosur geons, neuro-oncologists, neuro-radiologists, radiotherapists, and neurobiologists have taught us that the pathologist supplying the histological diagnosis may in fact some times fail to get across the biological message. Sometimes this failure arises because it is realy impossible for pathology to provide the expected nosographic definition of a tumor. Sometimes, by contrast, it is due to real difficulties in understanding the lan guage of the pathologist. This is particularly true when the prognosis deducible from the diagnostic label is not unequivocal. In attempting to be objective, the pathologist counterbalance the lack of a clear-cut definition with a detailed histological descrip tion, which means that everything depends upon his partners' ability to interpret this information properly. The aim of this book is thus to provide neuroligsts, neurosurgeons, neuro-oncolo gists and interested students of this subject with a broad knowledge base on the pathol ogy of brain tumors.