Synchronous bilateral neuroendocrine ductal carcinoma in situ.

Neuroendocrine ductal carcinoma in situ (NE-DCIS) is a breast malignancy that has characteristic clinicopathological features and can, therefore, be regarded as a distinct variant of DCIS. The patient was a 54-year-old premenopausal woman with hemorrhagic nipple discharge in her left breast. Magnetic resonance imaging and ultrasound (US) images of the left breast showed mass-like lesions, while concurrent images of the right breast showed non-mass-like lesions. These findings suggested the presence of both benign and malignant tumors. Pathological findings from US-guided core-needle biopsy of the left mass were highly suspicious of a malignant tumor. Excisional biopsy of both breasts was performed. We could define the diagnosis of breast cancer by the second opinion on pathological diagnosis. The tumor cells showed histological characteristics of NE-DCIS. Bilateral breast lesions had histopathological similarities and were composed of predominantly solid growth of carcinoma cells, frequently with well-developed vascular structures, in mammary ducts and ductules. Carcinoma cells were polygonal or occasionally spindle shaped and had fine-granular, relatively eosinophilic cytoplasm. The nuclei of these cells showed round to ovoid in shape and fine-granular chromatin pattern. There was not any invasive component, as confirmed by careful histological examination. Thus, additional immunohistochemical stainings for NE markers (chromogranin A and synaptophysin) were performed. Staining statuses of these markers were positive in almost all tumor cells from both breasts. Both tumors were therefore diagnosed as NE-DCIS. To our knowledge, this case is the first report of NE-DCIS diagnosed synchronously in both breasts.