Figure 6a. Fibroma of the tendon sheath in the foot of a 26-year-old woman. (a) Short-axis T2-weighted image depicts a mass, dorsal to the third metatarsal bone of the right foot, with signal that is hypointense to that of skeletal muscle. The anatomic location and signal intensity of the lesion are suggestive of a fibroma or giant cell tumor of the tendon sheath. (b) Photomicrograph (H-E stain) at high power shows a well-delineated mass that is hypocellular and contains a dense collagenous matrix that surrounds a slitlike vessel (arrow) and scattered spindle-shaped fibroblasts.