Usefulness of diffusion‐weighted imaging for differentiating between desmoid tumors and malignant soft tissue tumors

Purpose To evaluate the usefulness of diffusion‐weighted imaging (DWI) for differentiating between desmoid tumors and malignant soft tissue tumors. Materials and Methods Conventional MRI and DWI were performed for 8 desmoid tumors and 74 malignant soft tissue tumors. DWI was obtained with a single‐shot echo‐planar imaging sequence using a 1.5 Tesla (T) MR imager. DW images were acquired with motion‐probing gradient pulses applied along three directions (x, y, and z axes) with three b‐factors (0, 500, and 1000 s/mm 2 ). Two observers blinded to clinical information measured three regions of interest within the solid tumor and selected a minimum apparent diffusion coefficient () in each lesion. The mean ADC of desmoid tumors was calculated and compared with that of malignant soft tissue tumors using the Mann‐Whitney U test. Results The mean ADC of desmoid tumors and malignant soft tissue tumors was 1.36 ± 0.48 × 10 −3 mm 2 /s and 0.88 ± 0.20 × 10 −3 mm 2 /s (mean ± SD), respectively. The mean ADC of the desmoid tumors was significantly higher than that of malignant soft tissue tumors ( P < 0.01 ). Conclusion DWI is considered to be useful for differentiating between desmoid tumors and malignant soft tissue tumors. In the future, further investigation in a large series is necessary. J. Magn. Reson. Imaging 2011;33:189–193. © 2010 Wiley‐Liss, Inc.