Calcification in human breast carcinomas: Ultrastructural observations

Calcification in human breast carcinomas has been studied ultrastructurally. Multiple deposits of needle-shaped crystals intimately associated with electrondense material were observed among tumour cells. Similar deposits were present in intracytoplasmic lumina and the adjacent stroma. Cytoplasmic calcification was seen in membrane-bound vesicles and as partially membrane-bound clusters of crystals. It is suggested that the calcification is the result of an active secretory process rather than calcified necrotic or degenerate tumour cells. The possible mechanisms of calcification are discussed. Both electron diffraction and electron probe analysis show that the crystaline material is hydroxyapatite.