Sonographic Features of Extra-articular Giant Cell Tumor of the Tendon Sheath

The study aimed to retrospectively review sonographic features of extra-articular giant cell tumor of the tendon sheath (GCTTS), and developed a grouping system for facilitating differential diagnosis. From January 2005 to December 2009, 15 pathologically proven extra-articular GCTTS in 15 patients were encountered in our hospital. According to the tumor sites and their sonographic features, we categorized the sonographic findings into three types: superficial type (tumor attaching to the tendon but no complete encasement of it), encasing type (tumor completely encasing the tendon) and juxta-fascial type (tumor without attachment to the tendon). The demographic data, clinical presentation symptom, sonographic feature and color or power Doppler f low in each type of the patients were documented. Histopathologically, the localized or diffuse form of GCTTS was also recorded. The incidences of sonographic presentation in the superficial, encasing and juxta-fascial types of GCTTS were 46.7% (n=7), 33.3% (n=5) and 20.0% (n=3), respectively. The masses in the encasing type manifested with largest average size. The most common location of GCTTS in the superficial and encasing types was the hand. The 3 juxta-fascial type GCTTS were located in the subcutis of the hand and buttock, and the subfascial region of the forearm. On sonography, all GCTTS presented as hypoechoic masses with homogeneous or heterogeneous echogenicity. The tumors in the superficial and encasing types were eccentrically located to the related tendon and their superficial components were always disproportionally predominant. Bony erosion was found in three masses. No dermal attachment, decreased or increased sound through transmission, calcified or cystic component were noted in all masses. Only 26.7% of GCTTS demonstrated hypervascularity within the tumors. The two largest tumors were in encasing type and reported to be diffuse form microscopically. Two patients underwent recurrence, one with mass in superficial type and another in encasing type. We concluded that extra-articular GCTTS typically appears as a hypoechoic mass with heterogeneous or homogeneous echogenicity and intimate contact with the abutting tendon or fascia. The diffuse form GCTTS should be considered if a characteristic mass presented with larger size, lobulated or irregular contour, complete encasement of the related tendon and hypervascularity. Besides, differential diagnosis of a well-defined and fascia-attached mass should include juxtafascial type GCTTS.