Ultrastructural findings supporting the angioblastic nature of the so-called adamantinoma of the tibia.

Electron microscopy of a case of adamantinoma of the tibia shows features which support a mesenchymal angioblastic origin rather than epithelial. Comparison is made between tissue from this tumour and a squamous cell carcinoma of the femur arising in chronic osteomyelitis. In adamantinoma no desmosomes are found between tumour cells and their cytoplasmic ultrastructure shows features of mesenchymal cell type including evidence of pinocytic activity and bundles of filaments resembling hyperplastic endothelial cells. The stroma shows features similar to fibrous dysplasia of bone with fibroblasts, histiocytes and fibrolipoblastic lipid-laden mesenchymal cells. It is condluded that adamantinoma of the tibia should be considered to be an angioblastic tumour of bone.