A Case of Neuroendocrine Ductal Carcinoma In Situ of the Breast Detected as an Intra-Cystic Tumor Using Ultrasonography

We report a case of neuroendocrine ductal carcinoma in situ of the breast. The tumor was shown to be an intra-cystic tumor on performing ultrasonography. The patient was a 40-year-old woman. Amorphous calcifications were detected on her right breast on performing mammography during breast cancer screening. Ultrasonography indicated that the tumor was 9mm in diameter, and displayed features of an intra-cystic tumor. A vacuum-assisted core needle biopsy for breast tumor led to a diagnosis. The pathological diagnosis was mastopathy. We could not rule out malignancy of the tumor. Subsequently, we performed surgical resection with 5mm margins. The pathological diagnosis was intra-cystic neuroendocrine carcinoma in situ, positive for estrogen receptor and progesterone receptor, and negative for HER2/neu. The Ki-67 positive cell index was 5%. The surgical margin was negative. We performed a whole-body checkup, and confirmed a diagnosis of TisN0M0, Stage 0. She was initiated endocrine therapy with tamoxifen(20mg/day). Four years after surgery, she was well without metastases.