Primary Neuroendocrine Tumor of the Breast: Imaging Features
A 42-year-old female was presented with a lump in her right breast, which she had been aware of for several weeks. On physical examination, an approximately 5-cm, firm, movable lump was palpated in the upper outer subareolar region of her right breast. There was also a palpable, enlarged lymph node in the right axilla. Mammography revealed a high-density mass with an ill defined margin in the 11 o'clock direction of the right breast subareolar area. Right axillary lymphadenopathy was noted on the mediolateral oblique view. No microcalcification was detected on mammography (). Targeted sonography of the right breast revealed an irregularly shaped, lobulated marginated, heterogeneous echotextured mass with posterior enhancement. Heterogeneous echotexture was noted, especially in the center of the mass, and increased vascular flow was noted in the mass on color Doppler scanning. There was also lymphadenopathy in the right axilla with cortical thickening and loss of fatty hilum (). The mass was categorized as breast imaging reporting and data system category 5, highly suggestive of malignancy. Fine needle aspiration cytology revealed highly cellular smears with monotonous hyperchromatic atypical small cells, suggesting high-grade invasive ductal carcinoma. MRI of the breast was performed using a 1.5T system. The mass appeared to be of heterogeneously low signal intensity on T1 weighted images and a few parts of the mass showed intermediate to high signal intensity on T2 weighted images. The T2 non-high signal area showed rapid enhancement within the first two minutes of gadolinium injection, and washout was noted ().\nThe patient underwent a modified radical mastectomy and axillary dissection of the right breast. On the cut surface, the tumor appeared as a fairly well-defined but partially infiltrative, gray-white, solid mass with morphology similar to that of commonly seen, invasive ductal carcinoma. Histopathologically, several, large, mucoid, necrotic areas with foamy macrophages were surrounded by dark, solid, and trabecular pattern tumor cells. The tumor was composed of a mostly solid growth of large to intermediate, polygonal or occasionally spindle cells, which showed organoid, nesting, trabecular, rosette-like, and palisading patterns. Immunohistochemically, the tumor cells were diffusely positive for synaptophysin and were focally positive for chromograin A, although they were negative for CD 56. E-cadherin was demonstrated in cytoplasmic membranes (). Based on these pathology findings, we considered this tumor to be a large cell neuroendocrine carcinoma with atypical carcinoid features (histologic grade 3, T2N1M0, estrogen receptor [ER] [+], progesterone receptor [PR] [+], human epidermal growth factor receptor 2 [-]). Positron emission tomography - computed tomography after surgery showed an absence of abnormal uptake, suggesting that the breast was the only primary site.