MRI findings for differentiating benign and malignant soft tissue tumors: a systematic review—part 2: key imaging findings

OBJECTIVE: To synthesize magnetic resonance imaging (MRI) features and their reported diagnostic performance that differentiate benign from malignant soft-tissue tumors in alignment with the 2020 World Health Organization classification. MATERIALS AND METHODS: A systematic review was conducted in accordance with Preferred Reporting Items for Systematic Reviews and Meta-Analyses guidelines. PubMed, Embase, Scopus, and the Cochrane Central Register of Controlled Trials were searched through July 2024. Eligible studies reported MRI feature frequencies or diagnostic accuracy for common soft-tissue tumor subtypes. Reviews, case reports, duplicates, non-English publications, and studies outside the scope were excluded. Quality was assessed using the Quality Assessment of Diagnostic Accuracy Studies-2 (QUADAS-2). RESULTS: Seventy-six studies met inclusion criteria. In lipomatous tumors, homogeneous fat signal and thin septa supported lipoma, whereas thick or nodular septa and enhancement favored atypical or well-differentiated liposarcoma. Myxofibrosarcoma often demonstrated an infiltrative fascial "tail." Vascular lesions included angioleiomyoma with a reticular T2 pattern and glomus tumor with marked T2 hyperintensity and avid enhancement. In peripheral nerve sheath tumors, lower apparent diffusion coefficient values and peritumoral edema favored malignancy. Heterogeneity in imaging protocols precluded meta-analysis; results were summarized descriptively by subtype. CONCLUSION: Consolidated MRI patterns-such as septal morphology in lipomatous tumors, the fascial tail in myxofibrosarcoma, characteristic T2 patterns in vascular lesions, and diffusion and edema cues in nerve sheath tumors-support differentiation of benign and malignant entities, enhance reader confidence, and inform biopsy and management. Standardized prospective studies are needed to validate these thresholds and improve generalizability.