Added Value of Diffusion-Weighted Magnetic Resonance Imaging in Evaluation of Musculoskeletal Soft Tissue Masses

Abstract Background Magnetic Resonance Imaging is the method of choice for the diagnostic work- up of soft tissue tumors. It is the modality of choice to evaluate such masses, because of its excellent soft tissue contrast. Although there are some findings are indicative for malignancy, such as infiltration of adjacent tissues, destruction of bones and tendons, and the size of the mass, there are no criteria available to clearly distinguish benign masses from malignancies. Aim of the Work To evaluate the added value of diffusion-weighted magnetic resonance imaging in detection and characterization of musculoskeletal soft tissue masses. Patients and Methods This study is a cross-section hospital based retrospective study. This study conducted at Ain Shams University Hospitals. The main source of data for this study was the PET/CT scans and clinical history of the patients referred to the department of Radiology, Ain Shams University Hospitals and the period of the study is 12 months. Results Mean of enrolled patients was 37.1 ± 18.0 years and majority (72%) of them was females. It was noticed that thigh (28%) was frequently affect in the those patients followed by the leg (20%). Mean size of these masses was 101.14 ± 78.87 mm. based on histopathological evaluation of these mass; 15 (60%) masses were benign while malignant mass present in 10 (40%). Lipoma and Dermoid fibromatosis were the most frequent tumors in the current study (12%) following by Neurofibroma, Osteosarcoma, Sarcoma and Synovial sarcoma each one of them is (8%). Patients with malignant lesions had significantly lower ADC value in comparison to those with benign lesions (0.78 ± 0.09 vs. 1.56 ± 0.55 (10-3 mm2/s). Haemangiomas had the highest ADC value that was (2.35 ×10 − 3mm2/s.) while sarcoma had lowest value that was 0.54 ± 0.03 (103 mm2/s). It was noticed that MRI had 100% sensitivity and 93.3% specificity for diagnosis of malignant musculoskeletal soft tissue masses with overall accuracy was 96% and area under curve was 0.96 at cut off value was < 1.14 (103 mm2/s). Based on final diagnosis; MRI was successful in diagnosis of all cases with malignant musculoskeletal soft tissue masses but as the same time, MRI falsely diagnosed one case with benign nature to be malignant. Those one case was finally diagnosed to be lipoma. Conclusion The ability to differentiate benign musculoskeletal soft tissue tumors from malignant disease is limited clinically. Magnetic resonance imaging is an established modality for comprehensive diagnosis of musculoskeletal tumor. A non-invasive technique is needed to obtain information about the function of the tissue of interest. Diffusion-weighted (DW) MRI is an advanced technique used in combination with MRI to improve its diagnostic accuracy.