Benign fibrous histiocytoma of bone. Light- and electron-microscopic observations.

Case report of a patient with an unusual, rapidly growing bone tumor in the third and fourth cervical vertebrae. Histological and electron-microscopic investigations reveal a tumor composed of histiocytic cells, xanthomatous cells, giant cells of Touton type, and fibroblastic cells. No cellular features of malignancy are observed. From its cytologic appearance the tumor has to be classified as a benign fibrous histiocytoma. Regarding its ultrastructural features, the tumor may not be distinguished from non-ossifying fibroma of bone, but its clinical pattern shows obvious differences of localization and growth potential. the term "benign fibrous histiocytoma of bone" is proposed for these tumors which must be differentiated from non-ossifying fibroma.