Benign neck masses showing restricted diffusion: Is there a histological basis for discordant behavior?

Figure 5 Solitary fibrous tumour in a 24-year-old man. A: Coronal T2W image shows well defined left parapharyngeal space mass with heterogeneously hyperintense signal. The core is more hyperintense than the periphery. Multiple tortuous flow voids seen in the mass (solid arrows); B and C: DWI at b1000 (B) s/mm² and corresponding ADC map (C) show restricted diffusion in the periphery of the mass (dashed arrows) while the centre shows free diffusion (solid arrow); D: Photomicrographs show alternating cellular and hypocellular areas with abundant collagen (H-E; original magnification: × 200); E and F: Masson trichrome stain highlighting abundant collagen (E; original magnification: × 200); tumor cells are diffusely immunopositive for CD34 (F; original magnification: × 400). DWI: Diffusion weighted imaging; ADC: Apparent diffusion coefficient.