ReviewsDiagnostic Immunohistochemistry of Epithelial Lesions of the Breast A Review and an UpdateLegesse, Teklu MD; Ioffe, Olga B. MDAuthor Information From the University of Maryland Medical Center, Baltimore, MD. Reprints: Teklu Legesse, MD, University of Maryland School of Medicine, Department of Pathology, 22 Greene St, Baltimore, MD 21201. E-mail: [email protected]. The authors have no funding or conflicts to declare. AJSP: Review and Reports: January/February 2016 - Volume 21 - Issue 1 - p 11-15 doi: 10.1097/PCR.0000000000000126 Buy Metrics Abstract Histomorphologic evaluation is adequate for the appropriate assessment and classification of most breast lesions. In some cases, however, interpretation based on morphologic criteria alone may be difficult and subject to significant interobsever variability. In such circumstances, the use of immunohistochemistry aids in the proper evaluation of ambiguous and difficult lesions and helps avoid misclassification and mismanagement. This review describes the common uses and limitations of immunohistochemistry in the assessment of invasion, classification of intraductal proliferative lesions, distinction of lobular and ductal carcinoma, and evaluation of Paget disease of the nipple. The use of immunohistochemistry in the differentiation of spindle cell lesions of the breast, evaluation of metastasis from a possible breast origin, and the evaluation of papillary lesions are discussed in other reviews in this issue. © 2016 Lippincott Williams & Wilkins, Inc.