EMA (Epithelial Membrane Antigen/MUC1)

Epithelial membrane antigen (EMA) belongs to a heterogeneous family of highly glycosylated transmembrane proteins known as human milk fat globule (HMFG) membrane proteins. This family of antigens is not restricted to breast but may also be found in secretory epithelial cells, and in non-secretory epithelium such as squamous epithelium, and rarely in nonepithelial cells. EMA is considered a broad-spectrum antibody that is reactive against many types of adenocarcinoma. EMA can differentiate between the origins of glandular organs. Breast and skin adnexal tumours are strongly positive. In the identification of malignant mesothelioma, the distinct membranous EMA staining serves to distinguish from adenocarcinomas which frequently show a cytoplasmic staining pattern (1).

Recommended Controls

Criteria for acceptable staining is a cytoplasmic staining pattern. Recommended control to include kidney, breast and tonsil. Kidney will stain the epithelial cells of the collecting tubules but not the proximal tubules, while the Bowmans capsule will show weak to moderate positivity. In normal breast, EMA shows strong apical membranous staining of the luminal epithelial cells of ducts and lobules, consistent with its expression in secretory glandular epithelium. Tonsil should show strong cytoplasmic staining of superficial squamous epithelial cells and weak staining of plasma cells.

Expected staining pattern

Epithelioid mesothelioma

Breast cancer

Kidney

Breast

Tonsil

Disclaimer

These methods are intended as a guide only. Laboratories that wish to implement these methods should perform internal validation/verification prior to use. The RCPAQAP does not make any claim or warranty for the accuracy or performance of these methods.