James G. Smirniotopoulos, M.D.
Professor of Radiology, Neurology, and Biomedical Informatics
Chairman, Department of Radiology
and Nuclear Medicine
Uniformed Services University of the Health Sciences
4301 Jones Bridge Road
Bethesda, MD 20814
Carolyn Cidis Meltzer, M.D.
Director, PET Imaging Center
University of Pittsburgh
Visit us on the WEB: http://rad.usuhs.mil/
In 1993, the World Health Organization (WHO) published a revision of their book "Histological Typing of Tumours of the Central Nervous System" (1). This was a significant revision from the original work, issued first in 1979. The significance of this classification system is that it attempts, by consensus, to synchronize the organization and description of human neoplasms between countries and continents.
The 1993 revision represents a significant change and improvement from the original 1979 formulation. There are several new tumor types; but, some old familiar entities have either been eliminated or reclassified. The WHO system attempts to assign a numerical grade representing the overall biologic potential, on an ascending scale of malignancy of I (benign) to IV (malignant). It must be emphasized that since there are many well accepted histological tumor grading systems, this system should be identified when used (e.g. WHO Grade 1). Those familiar with the Kernohan/Sayre, AFIP, and Mayo/St. Anne's system should take comfort in the new WHO scheme because of many shared similarities. However, the new WHO system further stratifies some "benign" lesions into more than a single category. Low grade astrocytomas are now clearly divided into specific tumor subtypes, recognizing the unique favorable prognosis associated with juvenile pilocytic astrocytoma, subependymal giant cell astrocytoma, and several other variants. (1) (See Appendix 1)
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The opinions expressed herein are those of the author(s), and are not necessarily representative of the Uniformed Services University of the Health Sciences (USUHS), the Department of Defense (DOD); or the World Health Organization (WHO). Medicine is a constantly changing field, and medical information is subject to frequent correction and revision. Therefore the reader is entirely responsible for verifying the accuracy and relevance of the information contained herein.
Portions copyright 1997-2004 James
G. Smirniotopoulos, M.D.