Giant cell fibroblastoma in childhood immunohistochemical and ultrastructural study.

Two cases of giant cell fibroblastoma in children are presented. Histologic features included a dense fibrous tissue stroma with multinucleated giant cells lining sinusoid-like spaces. Immunohistochemical stains and electron microscopy provide evidence of a fibroblastic origin of the tumor cells. Ultrastructure of the multinucleated cells revealed segmentation of the nuclei with multiple centrioles, suggesting that an abnormality in the division of the tumor cells may be the mechanism for the formation of the giant cells.