Diffusion-weighted imaging in the assessment of tumour grade in endometrial cancer

Objective: Endometrial cancer is the most common gynaecological malignancy in developed countries. Histological grade and subtype are important prognostic factors obtained by pipelle biopsy. However, pipelle biopsy "samples'' tissue and a high-grade component that requires more aggressive treatment may be missed. The purpose of the study was to assess the use of diffusion-weighted MRI (DW-MRI) in the assessment of tumour grade in endometrial lesions. Method: 42 endometrial lesions including 23 endometrial cancers and 19 benign lesions were evaluated with DW-MRI (1.5T with multiple b-values between 0 and 750 s mm(-2)). Visual evaluation and the calculation of mean and minimum apparent diffusion coefficient (ADC) value were performed and correlated with histology. Results: The mean and minimum ADC values for each histological grade were 1.02 +/- 0.29 x 10(-3) mm(2) s(-1) and 0.74 +/- 0.24 x 10(-3) mm(2) s(-1) (grade 1), 0.88 +/- 0.39 x 10(-3) mm(2) s(-1) and 0.64 +/- 0.36 x 10(-3) mm(2) s(-1) (grade 2), and 0.94 +/- 0.32 x 10(-3) mm(2) s(-1) and 0.72 +/- 0.36 x 10(-3) mm(2) s(-1) (grade 3), respectively. There was no statistically significant difference between tumour grades. However, the mean ADC value for endometrial carcinoma was 0.97 +/- 0.31, which was significantly lower (p<0.0001) than that of benign endometrial pathology (1.50 +/- 0.14). Applying a cut-off mean ADC value of less than 1.28 x 10(-3) mm(2) s(-1) we obtained a sensitivity, specificity, positive predictive value and negative predictive value for malignancy of 87%, 100%, 100% and 85.7%, respectively. Conclusion: Tumour mean and minimum ADC values are not useful in differentiating histological tumour grade in endometrial carcinoma. However, mean ADC measurement can provide useful information in differentiating benign from malignant endometrial lesions. This information could be clinically relevant in those patients where pre-operative endometrial sampling is not possible.