Diffusion-weighted imaging of soft tissue tumors: usefulness of the apparent diffusion coefficient for differential diagnosis.

Purpose: We evaluated the efficacy of using the apparent diffusion coefficient (ADC) to differentiate soft tissue tumors.

Materials and methods: We examined 88 histologically proven tumors (44 benign, 8 intermediate, 36 malignant) using diffusion-weighted magnetic resonance images. Images of the tumors were obtained using a single-shot, spin-echo type echo-planar imaging sequence. The tumors were classified histologically as myxoid or nonmyxoid. We then compared the ADC values of the myxoid and nonmyxoid tumors; the benign and malignant myxoid tumors; and the benign, intermediate, and malignant nonmyxoid tumors.

Results: The mean ADC value of the myxoid tumors (2.08 +/- 0.51 x 10(-3) mm(2)/s) was significantly greater than that of the nonmyxoid tumors (1.13 +/- 0.40 x 10(-3) mm(2)/s) (P < 0.001). There was no significant difference in the mean ADC values between benign myxoid tumors (2.10 +/- 0.50 x 10(-3) mm(2)/s) and malignant myxoid tumors (2.05 +/- 0.58 x 10(-3) mm(2)/s). The mean ADC value of benign nonmyxoid tumors (1.31 +/- 0.46 x 10(-3) mm(2)/s) was significantly higher than that of malignant nonmyxoid tumors (0.94 +/- 0.25 x 10(-3) mm(2)/s) (P < 0.001).

Conclusion: The ADC value might be useful for diagnosing the malignancy of nonmyxoid soft tissue tumors.