Recurrent pulmonary metastases from benign giant cell tumors of the bone: report of two cases and analysis of nuclear DNA content by flow cytometry.

It is impossible to predict the biological characteristics of benign giant cell tumors of the bone (BGCTB) from light microscopic findings. About 2% of patients with BGCTB develop pulmonary metastases and we encountered two such patients, both of whom underwent several pulmonary resections. The nuclear DNA content of the primary lesion, the locally recurrent lesion, and the pulmonary metastatic lesions were determined by flow cytometry. The tumors from both patients exhibited a diploid pattern without any of the biological characteristics of BGCTB such as latent activity or metastasis.