Primary neuroendocrine carcinoma of the breast: clinical, imaging, and histologic features.

OBJECTIVE: The purpose of this study was to evaluate the clinical, imaging, and histopathologic findings of primary neuroendocrine carcinoma of the breast.
MATERIALS AND METHODS: A pathology database was searched for the records of patients with a histopathologic diagnosis of primary neuroendocrine carcinoma of the breast who had undergone mammography, sonography, or MRI between 1984 and 2011. The imaging studies of eligible patients were retrospectively reviewed according to the BI-RADS lexicon, and clinical presentation and histopathologic characteristics were documented. Imaging characteristics were compared with historical controls of invasive mammary carcinoma.
RESULTS: Eighty-seven patients (84 women, three men; mean age, 62.9 years; range, 28-89 years) were included in the study. The mean tumor size was 3.1 cm (range, 0.6-11 cm). Sixty-five of 84 (77.4%) cancers were estrogen and progesterone receptor positive and ERBB2 negative. A palpable mass (55.8%) was a common clinical manifestation. A high-density, round or oval, or lobular mass with nonspiculated margins on mammograms and an irregular (65.4%), hypoechoic (78.4%) mass, with indistinct margins (43.5%), no or enhanced posterior acoustic features (77.9%) on sonograms were common findings. MRI revealed an irregular mass (83.3%), irregular margins (63.6%), and washout kinetics (85.7%). Neuroendocrine carcinoma presented more frequently as masses on mammograms. Calcifications were infrequent compared with their occurrence in invasive mammary cancer.
CONCLUSION: Primary neuroendocrine carcinoma of the breast has mammographic features that differ from those of invasive mammary carcinoma. A round, oval, or lobular mass with nonspiculated margins, positive estrogen and progesterone receptor results, and negative ERBB2 results should raise suspicion of primary neuroendocrine carcinoma.