MRI Characteristics for Distinguishing Solitary Fibrous Tumor From Desmoid Tumor

To elucidate the magnetic resonance imaging (MRI) characteristics for distinguishing solitary fibrous tumors (SFTs) from desmoid tumors (DTs).

A retrospective study of 66 consecutive patients with histopathologically proven SFT (n = 34; 13 males and 21 females; mean age, 52.0 ± 17.1 years) or DT (n = 32; 11 males and 21 females; mean age, 39.0 ± 21.3 years) was conducted. The two groups were quantitatively compared in terms of the size, signal intensity ratio (SIR), and apparent diffusion coefficient value. For qualitative analysis, the tumor location, boundary, shape, internal uniformity, predominant signal intensity, T1-weighted images (T1WI) characteristics (hyperintense area), T2-weighted images (T2WI) characteristics (hypointense area, marked hyperintense area, flow void, band sign, and yin-yang sign), and contrast-enhanced T1WI characteristics (unenhanced area and degree of enhancement) were compared between the two groups. Multiple stepwise logistic regression analyses were conducted to distinguish between the SFT and DT.

T1 (P = 0.010) and T2 (P = 0.026) SIRs were higher in SFTs than in DTs. Hyperintense areas on T1WI (P < 0.001), marked hyperintense areas on T2WI (P = 0.025), and flow void (P = 0.025) were more frequently noted in SFTs. On T1WI, the solid component predominantly revealed hyperintensity in SFTs and isointensity in DTs (P < 0.001). Indistinct tumor boundary (P < 0.001), hypointense area on T2WI (P < 0.001), and band sign (P < 0.001) were more frequently observed in DTs. Multiple stepwise logistic regression analysis revealed that the hyperintense area on T1WI (odds ratio favoring SFT, 12.80, P = 0.002) and band sign (odds ratio favoring DT, 0.03; P < 0.001) were independent predictors.

MRI characteristics can help distinguish SFT from DT. The presence of a hyperintense area relative to the skeletal muscle on T1WI in SFTs and the band sign on T2WI in DTs are important MRI features.