Osteoblast like-cell identification. Ultrastructural analysis of breast cancer cells surrounding microcalcifications showed some elongated cells (LR-White embedding). (A) Toluidine blue stain on a semi-thin section of cells surrounding microcalcification in malignant lesions. (B) Electron micrograph obtained by TEM of cells shown in (A). (C) Ultrastructural details of cells obtained by immunogold reaction for vimentin. Numerous gold particles indicated the presence of vimentin filaments inside the cytoplasm of this cell (circle). (D) Electron micrograph obtained by TEM on electron-dense intracytoplasmic bodies in the analyzed cell. EDX spectrum confirmed these consisted of HA crystals (I). (E), (F), (G) and (H) present finer ultrastructural analysis of breast cancer cells surrounding microcalcifications, as performed on Epon-embedded tissue. (E) and (F) show ultrastructural details of a cell exhibiting osteoblast-like morphology with a large cytoplasm and a huge rough reticulum. (G) Cell near a microcalcification containing a HA-matrix vesicle. The enlargement in (G) and (H) capture a matrix vesicle just as it initiated the exocytosis of HA (EDX spectrum in (I) and (J)).