Material and Method: Between January 2008 and October 2014, 21 patients’ data and MRI findings were retrospectively reviewed by two musculoskeletal radiologists; data including sex, age, location of mass, number of lesion, size, shape, fatty component, adhesion to the tendon, signal intensity, neurovascular, and osseous involvement was recorded. The present study was approved by the Ethics Committee for Human Research of Khon Kaen University.

Results: The intra-observer and inter-observer reliability of MRI interpretation gave good agreements between two radiologists. Six patients had proven GCTTS and 15 patients had other benign soft tissue tumors, including four cases of hemangioma, four cases of lipoma, two cases each of fibroma and nodular fasciitis, and one case each of neulilemmoma, glomus tumor, and soft tissue chondroma. All GCTTS were solitary lesion with the diameter ranging from 1.2 to 6.4 cm, had well-circumscribed border and lobulation. All GCTTS were located at the volar aspect, attached to the flexor digitorum tendon. In MRI, they appeared as isointensity on T1-weighted images and hyperintensity on T2-weighted images with uniform or non-uniform enhancement. Osseous involvement was seen in all GCTTS cases. All other benign non-GCTTS showed variable MR characteristics. Two significant MRI findings on GCTTS were the presence of homogenous enhancement (p<0.01) and osseous involvement (p<0.04).

Conclusion: Benign soft tissue tumors in hand gave variable and overlapping MRI features. Two major MRI findings of GCTTS are the presence of uniform enhancement and/or osseous involvement. These two MRI features may be helpful for differential diagnosis of GCTTS among well-circumscribed lobulated soft tissue mass arising from the tendon of the hands.

Keywords: MRI, Hand, Giant cell tumor of tendon sheath, Hemangioma, Spindle cell lipoma, Neural lipoma, Neurilemmoma, Fibroma, Soft tissue chondroma, Glomus tumor, Nodular fasciitis