A non-invasive form of lipid-secreting carcinoma of the breast.

Lipid-secreting carcinoma is a rare variant of breast carcinoma. The tumor cells possess abundant vacuolated cytoplasm containing neutral fat. A 68-year-old Japanese female patient presented with a left breast tumor, which was detected by mass screening, and she was admitted to our hospital. The physical examination revealed an elastic hard lump in the left lateral quadrant of the left breast. The tumor size was 1.2 × 1.0 cm in diameter and the borderline was unclear. There were no palpable axillary lymph nodes or supraclavicular nodes. Mammography showed a polygonal mass with microcalcification. Ultrasonography indicated a hypoechoic lesion measuring 9 × 4 mm in diameter, with an irregularly shaped, slightly indistinct surface. The internal echoic level of the mass was heterogenous. Enhanced magnetic resonance imaging revealed a mass of high intensity in the left breast, and the connection of the intraductal spread was not detected. The time-intensity curve showed a peak-and-plateau pattern. Fine-needle aspiration cytology suggested a malignant tumor. The patient underwent a partial resection of the left breast (breast-conserving therapy) and a left axillary lymphadenectomy. Macroscopically, the resected specimen revealed a white tumor measuring approximately 0.6 × 0.5 cm. Histopathologically, the tumor measured up to approximately 0.9 × 0.7 cm because of additional components of intraductal spread and therefore was diagnosed as an extensive ductal carcinoma in situ with focal mass formation; the tumor also had abundant foamy cytoplasm. Oil-red-O staining confirmed the presence of marked cytoplasmic lipid droplets. These droplets were periodic acid-Schiff (PAS) negative even after diastase digestion, and negative with PAS-Alcian blue staining. In immunohistochemistry, these carcinoma cells were positive for E-cadherin. Thus, the pathological diagnosis was a non-invasive form of lipid-secreting carcinoma. The tumors were negative for both estrogen receptors and progesterone receptors. There were no metastases in the left axillary lymph nodes. The patient has remained well for 8 years without any evidence of recurrence.