Figure 5a. Fibroma of the tendon sheath in the hand of a 39-year-old woman. (a) Axial T2-weighted fast SE image shows a low-signal-intensity mass on the volar aspect of the thumb (arrow). The lesion has signal isointense to that of skeletal muscle. (b) Axial gadolinium-enhanced fat-suppressed T1-weighted fast SE image shows that the heterogeneously enhanced lesion involves the flexor pollicis longus tendon (arrow), which is anteriorly displaced.