OBJECTIVESTo retrospectively study on malignant giant cell tumor of tendon sheath (MGCTTS) in the hand, and to evaluate its clinical, histologic, immunohistochemical features and biologic evolution.

METHODSBetween January 1991 and December 2001, 10 patients with histologically proven MGCTTS were treated. The clinical material, radiographs and hematoxylin and eosin-stained sections were reviewed. Immunohistochemical studies and nuclear suspensions for flow cytometry were done on paraffin embedded tissue. All patients were followed up.

RESULTSThree of 10 patients in which the diagnosis of MGCTTS was originally considered were excluded after the slides reviewed and immunohistochemical examination performed. In the other 7 patients, one showed malignant and aggressive nature: the lesion recurred several times and the patient eventually died with pulmonary metastases. The immunohistochemical profile of the patient was similar to that reported in benign GCTTS, and the flow cytometry DNA analysis detected aneuploidy. Six cases presented histologic features of malignancy, 4 of them undertook the immunohistochemical examination and their profiles were similar to that reported in benign GCTTS. An aneuploidy DNA pattern was detected in one case on flow cytometry evaluation, diploidy DNA pattern was detected in 3 cases, and their S-phase fraction was 4.5%, 11.6% and 2.6% respectively. All of them had a benign clinical features, they were alive and without evidence of disease from 1.5 to 7.5 years (averagely, 4.5 years) after complete surgical excision or resections with wide surgical margins. None of them had received chemotherapy or radiation therapy.

CONCLUSIONSMalignant giant cell tumor of tendon sheath is an extremely rare malignant tumor, some cases have a poor outcome, the others, despite the histologically malignant features, have a good prognosis if wide surgical excision ablates the tumor completely.