Malignant giant cell tumor of soft parts.

Giant cell tumor of soft parts (GCTSP) is an extremely rare lesion with an unpredictable behavior. Some patients are cured with a simple surgical excision whereas others will develop metastatic disease within a relatively short interval. To date, there are no consistently reliable criteria, either clinical or histologic, to separate the benign from more aggressive lesions. We describe the clinical, histologic and radiologic features of a case with malignant behavior. The patient presented with a fungating skin and soft tissue mass and concurrent pulmonary nodules. The lesion recurred rapidly despite wide resection with negative surgical margins. Biopsy of the pulmonary lesions demonstrated metastatic disease.