CT and MRI Findings of Malignant Meningiomas: Comparison with Benign Meningiomas

ABSTRACT

PURPOSE: The purpose is to evaluate the CT or MRI findings to help in the differentiation between benign and malignant meningiomas. MATERIAL AND METHODS: The CT and MRI findings of 8 patients with surgically proven malignant meningioma were reviewed. Four cases of 8 malignant meningiomas and 18 cases of 27 benign lesions were studied with a 1.5T or 0.5T MRI. Radiologic analysis was focused on the heterogeneity of tumor, grade of peritumoral edema, presence of cystic degeneration and calcification, tumoral enhancement pattern, dural enhancement, and tumoral border. RESULT: Histologic types of malignant meningioma were meningotheliomatous (n=4), papillary(n=1), fibroblastic(n=l), angioblastic(n=l), and sarcomatous(n=l). Tumoral Heterogeneity was seen in 8 of 8 malignant lesions(100%) and 8 of 27 benign ones(30%). (p<0.01) Marked peritumoral edema was seen in 8 of 8 malignant lesions(100%) and 2 of 27 benign ones. (7.3%)(p<0.01) Most of malignant lesions(6 of 8 cases, 75%) showed ill defined border. Calcification was not present in malignant lesions in contrast with benign ones (14 of 27 cases, 52%). (p<0.05) No statistical significance was noted in cystic degeneration, dural tail like enhancement or tumoral enhancement pattern between malignant and benign meningiomas. MRI signal intensity of malignant meningiomas was homogeneously or heterogeneously hypointense on T1WI, heterogeneously isointense or hypointense on T2WI and heterogeneous or mixed on Gd-DTPA enhancement study. CONCLUSION: The CT or MRI findings such as heterogeneity, ill defined tumoral border, marked peritumoral edema, and absence of calcification may suggest the possibility of malignancy in meningioma.