Two cases of lipid-secreting carcinoma of the breast: case reports with an electron microscopic study.

Two very rare cases of lipid-secreting carcinoma of the breast are reported, together with a review of the literature. Both patients were Japanese women aged 70 and 81 years, respectively. In each, a mass had been found in the breast, and radical mastectomies were performed based on a diagnosis of breast cancer at an early clinical stage. Both resected tumors were found to be solid and localized. In them, both estrogen and progesterone receptors were negative. Microscopically, hematoxylin-eosin staining showed the tumor cells to have foamy and vacuolated eosinophilic cytoplasm. Lipid staining showed the vesicles in the cytoplasm of the tumor cells to be colored a flaming red and consequently recognized as lipid droplets. An electron-microscopic study showed that the tumor cells contained various sizes of lipid droplets in the cytoplasm with no degenerative changes, and suggested that these lipid droplets were produced and stored in the tumor cells. It would appear, from the literature that lipid-secreting carcinomas have aggressive clinical courses, but neither vascular invasion nor lymph node metastasis was seen in either of our two cases.