Neuroendocrine differentiation in breast carcinomas has been a matter of discussion since it was first described almost 60 years ago. Indeed, so-called neuroendocrine neoplasms of the breast (Br-NENs) are a less well-defined group of neoplasms than analogous entities in other anatomic sites, such as the lung and the gastroenteropancreatic (GEP) tract. Pure neuroendocrine phenotype is extremely rare, whereas the expression of neuroendocrine markers in usual breast carcinomas, both of special and of non-special type, without evident neuroendocrine morphology, is more common. In this context, the diagnostic criteria and the classification scheme for Br-NENs have been continuously changing over time and real consensus on this topic is still lacking, despite the recent publication of the 5th edition of the WHO classification of breast tumors. In this review, we will recapitulate the evolution of the concept of Br-NEN; revise the available knowledge on their morphological, molecular, and clinical features; and critically discuss the current classification scheme.

自从大约 60 年前首次描述乳腺癌的神经内分泌分化以来，它一直是一个讨论的问题。事实上，所谓的乳腺神经内分泌肿瘤 (Br-NEN) 与其他解剖部位（如肺和胃肠胰 (GEP) 道）中的类似实体相比，是一组不太明确的肿瘤。纯神经内分泌表型极为罕见，而神经内分泌标志物在通常乳腺癌中的表达更为常见，无论是特殊类型还是非特殊类型，没有明显的神经内分泌形态。在此背景下，尽管最近发布了第 5 版 WHO 乳腺肿瘤分类，Br-NEN 的诊断标准和分类方案一直在不断变化，但仍缺乏对该主题的真正共识。在这篇综述中，我们将概括 Br-NEN 概念的演变；修改有关其形态、分子和临床特征的现有知识；并批判性地讨论当前的分类方案。