Apocrine change is seen in a wide spectrum of breast lesions, ranging from microscopic cysts to invasive carcinoma. This article reviews the range of apocrine lesions and discusses the clinical significance of these lesions. Although apocrine change in many cases does not present any diagnostic difficulty, apocrine proliferations demonstrating cytologic atypia can be particularly challenging. The histologic criteria that have been proposed to foster reproducibility in categorizing such lesions are reviewed. This review attempts to clarify the terminology that has been applied to a range of benign lesions, including sclerosing adenosis and complex sclerosing lesions, containing foci of apocrine change. Malignant apocrine lesions, including both in situ and invasive carcinoma, are also discussed.