Characterization of Soft Tissue Tumors by Diffusion-Weighted Imaging

Diffusion-weighted imaging (DWI) is a noninvasive method for investigation of tumor histological content. It has been applied for some musculoskeletal tumors and reported to be useful. The aim of the present study was to prospectively evaluate the apparent diffusion coefficient (ADC) values of benign and malignant soft tissue tumors and to determine if ADC can help differentiate these tumors. DWI was performed on 25 histologically proven soft tissue masses. It was obtained with a single-shot echo-planar imaging technique using a 1.5T magnetic resonance (MR) machine. The mean ADC values were calculated. We grouped soft tissue tumors as benign cystic, benign solid or mixed, malignant cystic and malignant solid or mixed tumors and compared mean ADC values between these groups. There was only one patient with a malignant cystic tumor and was not included in the statistical analysis. The median ADC values of benign and malignant tumors were 2.31 ± 1.29 and 0.90 ± 0.70 (median ± interquartile range), respectively. The mean ADC values were different between benign and malignant tumors (P = 0.031). Benign cystic tumors had significantly higher ADC values than benign solid or mixed tumors and malignant solid or mixed tumors (p values were < 0.001 and 0.003, respectively). Malignant solid or mixed tumors had lower ADC values than benign solid or mixed tumors (P = 0.02). Our preliminary results have shown that although there is some overlap between benign and malignant tumors, adding DWI, MR imaging to routine soft tissue tumor protocols may improve diagnostic accuracy.