Assessment of the WHO classification of human meningiomas

Assessment of the WHO classification of human meningiomas Backer-Grøndahl T1, Torp SH1,2 1Dept. of Laboratory Medicine, Children’s and Women’s Health, Faculty of Medicine, NTNU 2Departement of Pathology and Medical Genetics, St. Olavs Hospital, Trondheim, Norway Background. Meningiomas comprise approximately one third of all intracranial tumors. They demonstrate a considerable heterogeneous histological picture. Most are benign and not expected to recur after surgical removal, however, up to 20 % of benign meningiomas do so. It is therefore a continuous work to refine classifications schemes to identify such tumours. Commonly used is that of the World Health Organization (WHO). This classification system has been regularly revised, last in 2007. Aim of the study. The aim of this study was to reassess the frequency of meningiomas of various malignancy grades using the WHO classification systems of 2000 and 2007. In addition an evaluation of prognostic histopathological factors was performed. Material and methods. A material of 196 primary, intracranial meningiomas treated at St. Olavs Hospital between 1991 and 2000 was revised and graded according to WHO 2000 and 2007 criteria. Histopathology was also correlated with clinical outcome. Results. The frequency of atypical (grade II) meningiomas was approx. 25 % and 30 % according to WHO 2000 and 2007 criteria, respectively. This increase was due to the definition of brain infiltrative meningiomas as atypical (grade II) in the latter. The prognostic value of established histopathological features was confirmed. Conclusion. Regular revision of classifications systems is essential to improve the diagnosis and prognosis of brain tumours.