[Preliminary studies on the ultrastructure of osteoid osteoma].

The ultra-structural appearance of osteoid osteoma is described. Significant features are; a well-developed endocytoplasmic reticulum, dilated cisterns in the cytoplasm of the osteroblasts, mineralized mitochondria from the cytoplasm of the osteoblasts and crystalline agglomerates on the vesicles rather than on the collagen network. The increased bone forming activity of the tissues of the osteoid osteoma is confirmed by the appearance of the osteoblastic cytoplasm. The presence of needle-like endomitochondrial crystals are further proof of enhanced osteoblastic function of the osteoid osteoma. Granular crystals appear when degenerative processes take place.