THERE has been considerable controversy about the malignant nature of xanthomatous giant cell tumors arising in soft tissues. Of the lesions noted in tendons and tendon sheaths Fleissig1 stated that there is no authentic record of metastatic growth. A similar conclusion has likewise been reached by Gomori2 and Bussebaum3 and by Berger4 in a more general appraisal of the problem. There have been, however, various indications that tumors of this nature may be malignant. Berger4 cited an example in which local invasive qualities were noted in a growth originating in the thigh. Tourneux5 reported an instance recorded by Gaudiani wherein a giant cell tumor metastasized to the regional lymph nodes. Similarly, he cited a case described by Dor, who treated a tumor on the index finger diagnosed as sarcoma myeloplaxes. This mass was excised, but it recurred locally and apparently then spread generally. Histologic