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Authors:  Dr Abdel Selim MBCHB , MS , PhD , FRCPath ¹ and Dr Ghada Elayat MBChB, MSc, PhD^2,3, 

1. Dr A Selim King’s College Hospital, Histopathology Department, Denmark Hill, London, UK. Abdel.Selim@nhs.net
2. Dr G Elayat Middlesex University, Department of natural science, Hendon, London, UK
3. Tanta University, Faculty of Medicine, Pathology Department, Tanta, Egypt G.Elayat@mdx.ac.uk

Abstract:

Apocrine metaplasia of the breast is a benign histological alteration characterised by the transformation of normal breast epithelial cells into cells with apocrine features. Although typically non-malignant, understanding this condition is essential for accurate diagnosis and patient management. This review aims to provide a comprehensive overview of apocrine metaplasia, including its histopathological characteristics, clinical significance, diagnostic approaches, differential diagnosis, molecular changes, ultrastructural characteristics, and management strategies. By synthesising current knowledge, this article aims to enhance awareness and facilitate informed decisionmaking among clinicians and researchers.

Keywords ::  apocrine metaplasia, breast, histopathology, diagnosis, molecular changes, ultrastructural characteristics, management

INTRODUCTION
The breast is a complex organ composed of various cell types, and benign proliferative changes can occur due to a myriad of factors. Apocrine metaplasia is one such benign alteration characterised by the transformation of breast epithelial cells into cells with apocrine features [1]. While typically nonmalignant, understanding apocrine metaplasia is crucial for accurate diagnosis and appropriate clinical management.
Histopathological Characteristics
Apocrine metaplasia is characterised histologically by the presence of large, eosinophilic, granular cytoplasm and prominent nucleoli in epithelial cells. These cells often exhibit decapitation secretion, a distinctive feature of apocrine differentiation. Immunohistochemical staining can further confirm the presence of apocrine differentiation markers, such as gross cystic disease fluid protein-15 (GCDFP-15) and androgen receptor (AR) [2].
Molecular Changes
Recent research has shed light on the molecular alterations underlying apocrine metaplasia. Dysregulation of various signalling pathways, including the androgen receptor (AR) pathway, has been implicated [3]. Overexpression of AR and its downstream targets has been observed in apocrine metaplasia, suggesting a potential role of androgen signalling in the pathogenesis of this condition. Furthermore, alterations in other signalling pathways, such as the PI3K/AKT/mTOR pathway, have also been identified [4].
Ultrastructural Characteristics
Ultrastructural analysis using electron microscopy provides valuable insights into the cellular architecture of apocrine metaplastic cells. Apocrine metaplastic cells typically exhibit abundant, irregularly shaped mitochondria, well-developed endoplasmic reticulum, and numerous microvilli on the cell surface [5]. Additionally, the presence of intracytoplasmic lumina and secretory granules can be observed, reflecting the apocrine nature of these cells.
Clinical Significance
Apocrine metaplasia is predominantly encountered in benign breast lesions, including fibrocystic changes, sclerosing adenosis, and papillomas. Although typically benign, apocrine metaplasia can occasionally coexist with atypical hyperplasiaor in situ carcinoma, necessitating thorough histopathological evaluation and clinical follow-up [6].
Diagnostic Approaches
The diagnosis of apocrine metaplasia relies on histopathological examination of breast tissue obtained via core needle biopsy or surgical excision. Additionally, immunohistochemical staining for apocrine markers, such as GCDFP-15 and AR, can aid in confirming the diagnosis [7].
Differential Diagnosis
Apocrine metaplasia must be distinguished from other breast lesions exhibiting similar histological features, including apocrine adenosis, apocrine carcinoma, and invasive carcinoma with apocrine differentiation. Careful examination of histological features and immunohistochemical staining patterns is essential for accurate diagnosis and appropriate clinical management [8].
Management Strategies
In most cases, apocrine metaplasia does not require specific treatment and can be managed conservatively with regular clinical follow-up. However, close monitoring is recommended, particularly in cases where apocrine metaplasia coexists with atypical hyperplasia or in situ carcinoma. Surgical excision may be warranted in selected cases for definitive diagnosis or symptomatic relief [9].

Citation:

A Selim. Exploring Apocrine Metaplasia of the Breast: A Short Review. Journal of Clinical Breast Cancer 2024