BackgroundNeuroendocrine carcinoma (NEC) of the breast is a rare type of carcinoma that has not been well studied or characterized. Of the limited number of studies reported in the literature, most are case reports. A few small retrospective series studies have been reported.MethodsWe reviewed data on 142 cases of mammary NEC recorded in the surveillance, epidemiology, and end results (SEER) database during 2003–2009 and evaluated disease incidence and patient age, sex, and race/ethnicity; clinicopathologic characteristics; and survival in comparison to invasive mammary carcinoma, not otherwise specified. We also performed univariate and multivariate analyses to identify prognostic factors in this disease.ResultsReview of the 142 SEER cases revealed that NEC is an aggressive variant of invasive mammary carcinoma. It generally occurred in older women (>60 years); present with larger tumor size (>20 mm), higher histologic grade, and higher clinical stage; and result in shorter overall survival and disease-specific survival than invasive mammary carcinoma, not otherwise specified (IMC-NOS). Overall survival and disease-specific survival were shorter in NEC at each stage than in IMC-NOS of the same stage. Furthermore, when all NEC and IMC-NOS cases were pooled together, neuroendocrine differentiation itself was an adverse prognostic factor independent of other known prognostic factors, including age, tumor size, nodal status, histologic grade, estrogen/progesterone receptor status, and therapy.ConclusionsNEC is a rare but aggressive type of mammary carcinoma. Novel therapeutic approaches should be explored for this uniquely clinical entity.

Our data demonstrate that a significant subgroup of ER/PR-negative and triple-negative breast cancers express FRA, and its expression is associated with worse clinical outcome.

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The clinical manifestations of IHE are non-specific. There is no significant correlation between histological type and prognosis. The clinicopathologic features of IHE in Chinese patients may provide a clue to further evidence-based studies.