Abnormal elastic fibers in elastosis of breast carcinoma. Ultrastructural and immunohistochemical studies.

Elastosis in benign and malignant breast lesions was studied by light microscopic immunohistochemistry for elastin and by electron microscopy. Upon immunohistochemical examination for elastin, elastosis, particularly in scirrhous-type ductal carcinoma, showed two characteristic staining patterns: fibrously and intensely stained elastic fibers and evenly stained elastic masses. Elastic fibers showing increased fibrous staining occurred mainly in the stromal areas, and were considered to be newly formed because they consisted of tannic acid-positive amorphous components and abundant microfibrils. Evenly stained elastic masses were observed mainly in the periductal areas and showed less intense stainability. These masses consisted of numerous fine amorphous components with plentiful microfibrils. In some regions within these masses, there were condensed accumulations of irregularly arranged small amorphous components associated with only a few microfibrils. These amorphous components had an ill-defined outline and were occasionally associated with spiralling collagen fibrils and cell debris. On the basis of these findings, the periductal evenly stained elastic masses were thought to be formed by excessive production of elastic fibers and degradation of pre-existing and newly formed elastic fibers.