Heterologous Metaplastic Carcinoma
Heterologous metaplastic carcinoma of the breast (same case as the previous two images). Highly atypical tumor cells are seen lining malignant osteoid matrix which is largely unmineralized (except for a small area near the top center and left). The intervening space between the osteoid trabeculae is filled with high-grade spindle cells. This tumor was composed entirely of spindle cells and heterologous elements.