Iron and neoplasia: ferritin and hemosiderin in tumor cells

Elevated serum ferritin levels have been reported in patients with malignant tumors and especially in those with neuroblastoma or breast carcinoma. The presence of the iron-storing compounds ferritin and hemosiderin in these tumors was therefore investigated. Some neuroblastomas, mostly of patients with advanced stages of disease, contained numerous ferritin particles randomly dispersed in the cytosol. Iron was also seen as ferritin clusters in the cytosol and as ferritin or hemosiderin in siderosomes. Morphometric study of ferritin particles as well as of the features of the siderosomes enabled the identification of two major types of iron-containing cells. In breast carcinoma most electron-opaque iron was found in siderosomes, with few ferritin particles being in the cytosol. The study points toward the hitherto unrevealed ultrastructure of cytosiderosis in neoplasms, the biological importance of which remains largely unknown.