Calcifying fibrous pseudotumor: an ultrastructural study.

To clarify the pathogenesis of calcification in calcifying fibrous pseudotumor (CFT), the lesion arising in the chest wall of a 16-month-old boy was ultrastructurally investigated. Fibroblasts were surrounded by large amounts of collagen fibrils. The dystrophic and psammomatous calcifications were observed as electron-dense amorphous masses and laminated bodies, respectively, within the cytoplasm of fibroblasts and in the collagenous stroma. The degeneration of cytoplasm seemed to be an initial event of intracytoplasmic calcification. Extracellular calcified substances often abutted to fibroblasts. Fibroblasts may play an important role in both intracellular and extracellular calcifications of CFT.