Assessment of infiltrative margins in subcutaneous soft-tissue sarcomas using ultrasonography and gadolinium-enhanced fat-suppressed T1-weighted imaging

Magnetic resonance imaging (MRI) aids in detecting infiltrative growth; however, preoperative determination of the extent of soft-tissue sarcoma (STS) infiltration remains challenging. Ultrasonography could also detect infiltration effectively. We investigated the usefulness of MRI and ultrasonography as preoperative assessments for infiltrative STS. We retrospectively evaluated the data of 24 patients with subcutaneous infiltrative STS. Infiltrative length was measured using gadolinium-enhanced fat-suppressed T1-weighted imaging (GdFsT1) (M-IL) and ultrasonography (U-IL). The reactive layer was set at a greater distance of M-IL or U-IL. The surgical margin was set at greater distance of 2 cm from the tumor edge or 1.5 cm beyond the reactive layer. Histological infiltrative length (H-IL) and histological surgical margin length (H-margin) were measured using specimens. Relationships among M-IL, U-IL, and H-IL were analyzed using Spearman's rank correlation coefficients. Clinical outcomes, such as overall survival (OS) and local recurrence (LR), were evaluated using the Kaplan–Meier method. In 19 of 64 directions, H-IL was wider than M-IL. Among the 19 directions, U-IL was wider than H-IL in 11 directions, whereas H-IL was wider than U-IL in 8 directions. Mean H-margin was 29 mm, and the margin was negative in all directions. Spearman's correlation revealed weak associations between H-IL and M-IL (ρ = 0.08, p > 0.05) and H-IL and U-IL (ρ = 0.16, p > 0.05). The 5-year LR and OS were 91% and 87.5%, respectively. GdFsT1 alone underestimated STS infiltration. Combined MRI and ultrasonography represent a feasible approach for preoperative assessment and aids in achieving margin-negative resection for subcutaneous STS.