Is diffusion-weighted imaging useful in grading and differentiating histopathological subtypes of meningiomas?

PURPOSE: Meningiomas are mostly benign, however atypical or malignant subtypes with more aggressive clinical course and higher recurrence rates can also be seen. The purpose of this study was to determine whether histopathological subtypes of meningiomas could be assessed preoperatively using apparent diffusion coefficient (ADC) values.
MATERIALS AND METHODS: Conventional magnetic resonance (MR) and diffusion-weighted (DW) imaging of 177 adult patients with pathologically proven meningiomas were retrospectively evaluated. Tumor size and the degree of associated edema were noted. The signal intensity of the lesions on DW imaging was evaluated and graded. Mean ADC values were obtained as the mean of measurements from three regions of interests within the mass. ADC ratios of meningioma/contralateral normal appearing subcortical parietal white matter were also calculated.
RESULTS: The histopathological analysis revealed 135 benign, 37 atypical and 5 malignant lesions. With classification according to the subtype, the mean ADC values and ratios of benign meningiomas were as 0.99±0.12×10(-3) mm(2)/s and 1.22±0.07, respectively. ADC values for atypical and malignant groups were both 0.84±0.1×10(-3) mm(2)/s. The ADC ratios were 1.05±0.1 and 0.96±0.2 for atypical and malignant subtypes, respectively. There was no statistically significant difference between the mean ADC ratios of the three subtypes (ANOVA test; P≥0.05). Gender, age of the patients and tumor size showed no statistically significant difference between the different histological groups.
CONCLUSION: DW MR imaging was not found to have any additional value in determining histological behaviour nor in differentiating histopathological subtypes of meningiomas.