Comprehensive analysis of clinicopathologic features and p53 mutation in neuroendocrine neoplasms of the breast: experience from a large academic center

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. Conclusion: NECs of the breast are genetically and clinically different from IBC-NST-NEs and NETs of the breast.