This study investigated the clinical usefulness of diffusion-weighted imaging (DWI) and the apparent diffusion coefficient (ADC) value for preoperative differentiation between uterine leiomyoma and leiomyosarcoma.

This study included 10 lesions from 5 patients with pelvic leiomyosarcoma and 83 leiomyoma nodules from 76 patients, as identified by postoperative pathological examination (1 autopsy). All magnetic resonance examinations were performed with a 1.5-T superconductive magnetic resonance unit.

The leiomyosarcoma lesions were readily apparent via DWI, presenting as an intermediate- to high-intensity area in the uterine wall. All low-intensity areas presented as leiomyoma nodules. The mean ADC value for the 10 leiomyosarcoma lesions was 0.791 ± 0.145 (×10⁻³ mm²/s), significantly lower than that of the leiomyoma nodules that presented with intermediate-intensity areas, 1.472 ± 0.285 (×10⁻³ mm²/s) (n = 41) (P < .001), and high-intensity areas (1.100 ± 0.343) (n = 9) (P = .03). Additionally, in this study, the highest ADC value for a leiomyosarcoma was 1.095, with an intermediate DWI intensity. Based on these results, we classified the patients into 2 groups: low-risk group (barely any leiomyosarcoma risk) and high-risk group. Analyses comparing the 2 groups yielded the following: sensitivity, 100%; specificity, 94.0%; positive predictive value, 66.7%; negative predictive value, 100%; and accuracy, 94.6%.

We suggest that this modality using a combination of signal intensity on DWI and ADC value is very effective, simple, and easy to apply clinically for differential diagnosis of leiomyosarcoma and myoma.