Giant Cell Tumor of the Tendon Sheath, Hand

28-year-old male with a history of swelling of the small finger of the right hand and palmar pain. There is an infiltrative lobular T1 isointense to skeletal muscle lesion which is STIR hyperintense and heterogeneously enhancing. The lesion is intimately associated with the extensor compartment tendon of the small finger as well as the palmar flexor tendons. The lesion demonstrates well circumscribed borders. The imaging findings are characteristic for a giant cell tumor of the tendon sheath. Giant cell tumors are uncommon and usually benign lesions arising from the tendon sheath. They are usually well localized, solitary, subcutaneous soft tissue nodules with low T1 and T2 signal intensity and moderate enhancement. Differential includes ganglion cyst, demoid tumor, and fibroma. Primary surgical resection is treatment of choice.