Skin metastasis from conventional giant cell tumor of bone: conceptual significance

A conventional giant cell tumor of the proximal femur recurred twice locally and developed pulmonary nodules. The lung lesions were felt to be an example of "benign" metastases. Eight months after the initial presentation, the patient developed a single skin nodule on the contralateral leg. Histologic features of the skin nodule showed conventional giant cell tumor identical to the bone lesion. This nodule is a manifestation of arterial metastasis typical of any malignant tumor and seemingly contradicts the concept of "benign" metastasis.