Common uses of immunohistochemistry in interpreting lesions of the breast: a pictorial review

The present pictorial review includes a brief explanation of the basic principles involved in immunohistochemistry and an overview of its use as a problem-solving and prognostic tool in the context of breast disease.

Myoepithelial markers cytokeratins 5/6, p63 and smooth muscle actin are helpful in distinguishing lesions that mimic invasion, namely radial scar and sclerosing adenosis from invasive lesions. These markers can also be used in differentiating intraductal papilloma from papillary carcinoma, and their patterns of expression can help distinguish ductal carcinoma in situ from atypical ductal hyperplasia. Epithelial markers such as AE1/AE3 and cytokeratin 7 may identify subtle foci of stromal invasion and micrometastasis in lymph nodes. Each of the above scenarios is illustrated with radiological and pathological images, and shows the role of immunohistochemistry in attempting to resolve these diagnostic dilemmas.

The role of this technique in the typing of certain breast tumours is discussed and illustrated using E-cadherin in distinguishing ductal from lobular carcinoma.

Finally, the prognostic role of immunohistochemistry in oestrogen receptor, progesterone receptor and human epidermal growth factor receptor 2 analysis for primary breast carcinomas is illustrated.