Pathodiagnostic Parameters for Meningioma Grading

Meningiomas are usually slow-growing benign tumors, for which complete removal can be difficult and recurrence is an issue. In this study the relationship between pathodiagnostic parameters, histological grade, and MIB-1 monoclonal antibody expression in meningioma diagnosed over 10 years in Shohada Hospital, Tehran, was assessed. All cases were re-evaluated according to the latest World Health Organization (WHO) Classification. Between January 1997 and December 2006, a total of 4885 intracranial tumors were diagnosed at Shohada Hospital, 378 (7.74%) of which were meningiomas. All slides stained with hematoxylin and eosin were reviewed by two independent pathologists and all the diagnoses reconfirmed; histological anaplasia was classified according to the grading of the WHO Working Group 2000 as benign (Grade I), atypical with incipient signs of anaplasia (Grade II), or overtly anaplastic (Grade III). The mean age of patients with meningiomas was 49.11+/-12.99 years (range 6-78 years, median=50); females outnumbered males by a ratio of 1.7 to 1. Presenting symptoms were headache/vertigo (66.7%) and epilepsy (28.5%). Convexity meningiomas were most common, followed by meningiomas of the sphenoid ridge and cerebellopontine angle. There was no relationship between the location of the tumor and the histopathological features. The association between mitotic rate, increased cellularity, nucleo-cytoplasmic ratio, and sheet-like spreading was especially strong. Histopathological study of completely resected meningiomas showed that loss of architecture, frequent mitotic figures, a high cellularity, increased nucleo-cytoplasmic ratio, a prominent nucleolus, brain invasion, and necrosis were correlated with the grade of the meningiomas. Overall, the mitotic count was the most important marker for tumor grade.