Non-ossifying fibroma or benign lipoblastoma of bone--an electron-microscopic and histochemical study.

An ultrastructural and histochemical analysis was made of a lesion identified by light microscopy as a non-ossifying fibroma of bone. A histogenetic sequence was traced from spindle-shaped fibroblast-like cells to multivacuolated lipoblasts with abundant glycogen. These lipid-laden cells showed remarkable similarity to some cells of a well differentiated liposarcoma. Others have interpreted the lipid-containing cells of non-ossifying fibroma as representing fibroblasts which have imbibed or synthesized lipid or lipid-laden macrophages. Our studies demonstrate that this tumour consists of primitive mesenchymal cells with partial maturation to early lipoblasts, suggesting its classification as a benign lipoblastoma of bone.