Comprehensive Analysis of Clinicopathologic Features and p53 Mutation in Neuroendocrine Neoplasms of the Breast: Experience from a Large Academic Center

Abstract Purpose The recent WHO classification of breast cancer (2019) categorizes breast carcinoma with neuroendocrine (NE) differentiation into three morphologically distinct subtypes: well-differentiated neuroendocrine tumor (NET), poorly differentiated neuroendocrine carcinoma (NEC), and invasive breast carcinoma, no special type with neuroendocrine differentiation (IBC-NST-NE). Data regarding the prognostic significance of neuroendocrine differentiation are conflicting and an association, if any, between p53 mutation and neuroendocrine differentiation is largely unknown. Methods We examined p53 expression and other clinicopathologic characteristics in three types of invasive breast carcinoma with NE differentiation in a cohort of sixty-three patients, including 45 IBC-NST with NE differentiation, 10 NETs and 8 NECs. Results No significant difference of clinicopathologic feature was observed between IBC-NST with NE differentiation and NET, but NECs showed significantly lower expressions of hormone receptors, more mutated p53 and higher frequency of distant metastases than IBC-NST with NE differentiation and NETs.Conclusions NECs of the breast are genetically and clinically different from IBC-NST-NEs and NETs of the breast.