y Conventional MR and diffusion-weighted imaging of musculoskeletal soft tissue malignancy: correlation with histologic grading

AimTo evaluate proven soft tissue musculoskeletal malignancies blinded to their Federation Nationale des Centres de Lutte Contre le Cancer histologic grades to identify the predictive values of conventional MR findings and best fit region of interest (ROI) apparent diffusion coefficient (ADC) measurements.Materials and methodsFifty-one consecutive patients with different histologic grades were evaluated by four readers (R1-4) of different experience levels. Quantitatively, the maximum longitudinal size, tumor to muscle signal intensity ratios, and ADC measurements and, qualitatively, the spatial location of the tumor, its signal alterations, heterogeneity, intralesional hemorrhage or fat, and types of enhancement were assessed. Intraclass correlation, weighted kappa, ANOVA, and Fisher exact tests were used.ResultsThere were 22/51 (43%) men (mean ageSD=5216years) and 29/51 (57%) women (mean ageSD=5417years), with the majority of tumors 38/51 (75%) in the lower extremities. Histologic grades were I in 8/51 (16%), II in 17/51 (33%), and III in 26/51 (51%), respectively. The longitudinal dimensions were different among three grades (p=0.0015), largest with grade I. More central enhancements and deep locations were seen in grade III tumors (p=0.0191, 0.0246). The ADC mean was significantly lower in grade III than in grade I or II (p<0.0001 and p=0.04). The ADC min was significantly lower in grade III than in grade I (p=0.02). Good to excellent agreements were seen for T1/T2 tumor/muscle ratios, longitudinal dimension, and ADC (ICC=0.60-0.98).Conclusion Longitudinal tumor dimension, central enhancement, and ADC values differentiate histology grades in musculoskeletal soft tissue malignancy with good to excellent inter-reader reliability.Key Points center dot The longitudinal tumor dimension of grade III malignancy is smaller than that of grade I (p<0.0001), and higher-grade tumors are located deeper (p=0.0246). center dot The ADC mean is significantly lower in grade III than in grade I or grade II (p<0.0001 and p=0.04). center dot The ADC minimum is significantly lower in grade III than in grade I (p=0.02).