IntroductionG iant cell tumor of tendon sheath (GCTTS) and ganglion cyst are the most common benign tumors of the hand (1, 2). In general GCTTS can present as a solitary subcutaneous nodule of the hand, but it can also occur in other parts of the body such as the spine, ankle, knee and feet (3, 4). However, with an approximate incidence of 1/50,000 per population it remains an uncommon condition (5). The incidence of GCTTS is higher in women than in men and mostly seen in the third to fifth decade (3, 6).The results of previous research are inconsistent regarding whether GCTTS is more often volar or dorsal in the hand, with a tendency for it to occur more often on the volar aspect of the hand (7-10). The occurrence of a volarsided GCTTS has been reported to range between 44 and 76% (7-11). The purpose of this study was to examine a large series of GCTTS in the hand to further assess the relative frequency of dorsal and volar GCTTS. We hypothesized that GCTTS are equally common on the dorsal and volar aspects of the hand. In addition, we hypothesized that there are no factors (i.e., demographic, clinical and pathological) associated with the location (volar versus dorsal side) and largest measured diameter of a GCTTS. Materials and MethodsUnder an IRB approved protocol 278 patients that had operative treatment of a GCTTS between January 2002 and November 2012 were identified using a database of pathology reports. The study was performed in a single tertiary care hospital and the procedures were performed by four experienced hand surgeons. Informed consent was waived for this medical record study. The medical records of all patients aged 18 years or older with a pathologically confirmed GCTTS of the finger or hand were reviewed retrospectively. Pregnant women (IRB mandated) and patients with a recurrence of a GCTTS already surgically treated in our center were excluded. We recorded sex, age, side, dorsal or volar location, finger or hand location and largest measured diameter of the GCTTS. The diameter was obtained from the pathology report. Giant Cell Tumor of Tendon SheathAbstract Background: Giant cell tumor of tendon sheath (GCTTS) is often thought of as a volar finger mass. We hypothesized that GCTTS are equally common on the dorsal and volar aspects of the hand. In addition, we hypothesized that there are no factors associated with the location (volar versus dorsal) and largest measured dimension of a GCTTS.