Fibroepithelial Tumors of the Breast Pathologic and Immunohistochemical Features and Molecular Mechanisms

Context.-The 2 main prototypes of fibroepithelial tumors of the breast include fibroadenoma and phyllodes tumor (PT). Although both tumors share some overlapping histologic features, there are significant differences in their clinical behavior and management. Phyllodes tumors have been further divided into clinically relevant subtypes, and there is more than one classification scheme for PT currently in use, suggesting a lack of consistency within different practices. Accurate differentiation between fibroadenoma and PT, as well as the grading of PT, may sometimes be challenging on preoperative core needle biopsy. Some immunohistochemical markers have been suggested to aid in the pathologic classification of these lesions.Objective.-To discuss the salient histopathologic features of fibroepithelial tumors and review the molecular pathways proposed for the initiation, progression, and metastasis of PTs. Also, to provide an update on immunohistochemical markers that may be useful in their differential diagnosis and outline the practice and experience at our institution from a pathologic perspective.Data Sources.-Sources included published articles from peer-reviewed journals in PubMed (US National Library of Medicine).Conclusions.-Fibroepithelial tumor of the breast is a heterogenous group of lesions ranging from fibroadenoma at the benign end of the spectrum to malignant PT. There are overlapping histologic features among various subtypes, and transformation and progression to a more malignant phenotype may also occur. Given the significant clinical differences within various subtypes, accurate pathologic classification is important for appropriate management. Although some immunohistochemical markers may be useful in this differential diagnosis, histomorphology still remains the gold standard.

背景：乳腺纤维上皮性肿瘤的两种主要原型包括纤维腺瘤和叶状肿瘤（PT）。尽管这两种肿瘤具有一些重叠的组织学特征，但它们在临床行为和处理上存在显著差异。叶状肿瘤进一步被分为具有临床相关性的亚型，且目前使用的PT分类方案不止一种，这表明不同实践之间缺乏一致性。在术前粗针穿刺活检中，纤维腺瘤和PT之间的准确鉴别以及PT的分级有时可能具有挑战性。一些免疫组化标记物已被建议用于辅助这些病变的病理分类。 目的：讨论纤维上皮性肿瘤的显著组织病理学特征，回顾为PT的起始、进展和转移所提出的分子途径。此外，提供可能有助于其鉴别诊断的免疫组化标记物的最新情况，并从病理角度概述我们机构的实践和经验。 数据来源：来源包括PubMed（美国国立医学图书馆）中经同行评审的期刊上发表的文章。 结论：乳腺纤维上皮性肿瘤是一组异质性病变，从良性一端的纤维腺瘤到恶性的PT不等。各种亚型之间存在重叠的组织学特征，并且也可能发生向更恶性表型的转变和进展。鉴于各种亚型之间存在显著的临床差异，准确的病理分类对于恰当的处理是重要的。尽管一些免疫组化标记物可能有助于这种鉴别诊断，但组织形态学仍然是金标准。