Chondroblastoma of the scapula.A case report with ultrastructural observations

A large chondroblastoma of the scapula, with articular and soft-tissue extension, the fourth recorded in this location, was removed by forequarter amputation in a 29-year-old man after 12 years of growth. Ultrastructurally, die typical chondroblastoma cells was characterized by indented, multilobular nuclei with narrow peripheral bands of electron-dense substance, by a subdivision of the cytoplasm into an electron-dense endoplasm containing most of the organelles and an electron-lucent ectoplasm largely devoid of structured components, by fine intracytoplasmic fibrils frequently forming dense band-like aggregates between endo-and ectoplasm, and by numerous blunt microvilli at the cell surface. Also present were fusiform cells of uncertain nature and multinudeated giant cells of foreign body or osteoclastic type. The interstitium contained collagen and thin reticular fibrils; the latter appeared to be a product of the tumor cells. The observed ulaastructural features support the view that chondroblastoma is a tumor derived from cartilage-forming matrix cells.