Diagnostic value of the apparent diffusion coefficient in differentiating malignant from benign endometrial lesions

Abstract

Introduction: Magnetic resonance imaging (MRI) with its innovative techniques, such as diffusion-weighted imaging (DWI) and apparent diffusion coefficient (ADC), increases the diagnostic accuracy in distinguishing between malignant and benign lesions of the endometrium. The aim of the study was MRI differentiation between malignant and benign endometrial lesions and correlation with histopathological findings with a special emphasis on quantitative analysis. An additional aim was to correlate the ADC values and histological tumor grades.

Methods: The prospective study included 119 female patients with or without vaginal bleeding and pathological values of endometrial thickness, who underwent MRI examinations. According to MRI reports the patients were divided into 45 suspicious malignant and 74 suspicious benign endometrial lesions. The radiological diagnosis was compared to the histopathological evaluation, which confirmed 37 malignant lesions while the rest were benign.

Results: The mean ADC value for malignant lesions was 0.761 ± 0.13×10^-3 mm²/s and for benign lesions was 1.318 ± 0.20×10^-3 mm²/s. The ADC values for malignant lesions were expectedly lower than those of benign lesions (p<0.001). The ADC cut-off value was 1.007×10^-3 mm²/s with a sensitivity of 100%, specificity of 92.7%, a positive predictive value of 60.3%, and a negative predictive value of 100%. In comparison with the histopathological findings, the sensitivity of MRI was 100%, specificity 90.2%, positive predictive value was 82.2%, and negative predictive value was 100%. Observing the histological grades 1, 2, and 3 of endometrial carcinoma, no statistically significant differences of mean ADC values were found. The mean ADC values for histological tumor grades 1,2 and 3 were 0.803 ± 0.13×10^-3 mm²/s, 0.754 ± 0.12×10^-3 mm²/s and 0.728 ± 0.13×10^-3 mm²/s, respectively.

Conclusion: DWI and ADC values represent clinically useful tools for the differentiation between malignant and benign endometrial lesions with high sensitivity and good specificity, but the results failed to demonstrate their usefulness in differentiating histological grades of endometrial cancer.

Keywords: diffusion magnetic resonance imaging; endometrial cancer; endometrium; gynecology; pathology.

Figure 1

The general flowchart shows the methodological steps of the study.

Figure 2

MR images of a 55-year old woman with a history of vaginal bleeding, high suspicious EC on MRI, and histopathologically proven endometrial endometrioid carcinoma, HG2 (FIGO stage II): (A) sagittal and (B) axial T2W FR FSE image shows endometrial mass (arrow) in uterine cavity which is hyperintense on axial DWI (b=1200 s/mm²) (C) and has correlation on ADC map with the measured ADC value of 0.817 × 10⁻³ mm²/s (D).

Figure 3

MR images of a 66-year old woman with a history of vaginal bleeding, suspicious benign lesion on MRI, and histopathologically proven endometrial hyperplasia: (A) sagittal and (B) axial T2W FR FSE image shows thickened endometrium in uterine cavity (arrow) which is slightly hyperintense on axial DWI (b=1200 s/mm²) (C) and has no correlation on ADC map with the measured ADC value of 1.792 × 10⁻³ mm²/s (D).

Figure 4

The box-and-whisker plots show the ADC values of benign and malignant endometrial lesions according to histopathological analysis.

Figure 5

ROC curve analysis of ADC values in differentiation between malignant and benign endometrial lesions.

Figure 6

Comparison of the ROC curves of ADC values (blue curve) and endometrial thickness measured by TVUS (green curve) in differentiation between malignant and benign endometrial lesions.

Figure 7

The box-and-whisker plots show the ADC values in different histological grades (G1, G2, and G3) of malignant lesions.