This study aimed to evaluate the efficacy of using MRI findings to differentiate superficial spindle cell lipomas (SCLs) from atypical lipomatous tumor/well-differentiated liposarcomas (ALT/WDLs).

This study included 12 patients with histopathologically proven superficial SCLs and 11 with ALT/WDLs. MRI findings for both pathologies were retrospectively reviewed and compared between the two pathologies.

The neck, upper back, and shoulder regions were more frequent locations of SCLs than of ALT/WDLs (100% vs 55%, p < 0.05), whereas no significant differences were observed in age and sex. The median maximum diameter of the lesion was smaller in SCLs than in ALT/WDLs (44 mm [IQR: 35–63] vs 102 mm [IQR: 86–119], p < 0.05). On T1-weighted images, non-fatty area was more frequently observed in SCLs than in ALT/WDLs (73% vs 25%, p < 0.05), and the median rate of non-fatty area was larger in SCLs than in ALT/WDLs (7.5% [IQR: 1.0–53] vs 0% [IQR: 0–0.2], p < 0.05). On fat-suppressed T2-weighted images, a solid hyperintense area was more frequently observed in SCLs than in ALT/WDLs (83% vs 27%, p < 0.05).

The maximum diameter, non-fatty area on T1-weighted images, and solid hyperintense area on fat-suppressed T2-weighted images were useful imaging features for differentiating superficial SCLs from ALT/WDLs.

In superficial lipomatous tumors, small tumor size and non-fatty solid area were valuable findings for diagnosing SCLs..