Metaplastic lipid‐rich carcinoma of the breast

A case of lipld-rich mammary carcinoma identified in a lumpectomy specimen from a 56year-old female is presented. The tumor showed features of poorly differentiated invasive ductal carcinoma of clearcell phenotype. Cytoplasmic lucency was mainly accounted for by the accumulation of neutral fat and, to a lesser degree, glyco-gen. Tlnctorial properties Included positivity of tumor cells with Sudan iii dye and diastasesensitive periodic acid-Schiff staining. Ultrastructural examination confirmed the presence of abundant cytoplasmic lipid droplets and some glycogen rosettes. On immunohistochemistty, most tumor cells reacted for cytokeratin, vimentin and S-100 protein, and there was focal expression of carclnoembryogenic antigen. A minority of tumor cell nuclei expressed progesterone receptors. As an additional feature, part of the leslon exhibited chondroid metaplasia. Lipid-rich carcinoma of the breast is exceedlngly rare and, to our knowledge, no such example harboring metaplastic elements has been described previously.