Histo: paucicellular tumor with scattered spindle-shaped myofibroblasts embedded in dense collagenous stroma + slitlike vascular channels and cleftlike spaces = crossover to giant cell tumor of tendon sheath

Mean age: 31 (range, 20–50) years; M÷F = 2÷1

Location: tendon sheath of upper extremity (fingers, hands, wrists) in 82%

Size: usually <3 (range, 1–5) cm

• mostly painless soft-tissue mass

MR:

• small hypointense nodule on all pulse sequences compared to muscle
• areas of high signal intensity ← myxoid change
• no / moderate / marked enhancement
• attachment to tendon sheath

Rx: local excision (24% recurrence rate)

DDx: giant cell tumor of tendon sheath (blooming artifact ← hemosiderin deposition)