Epithelial Membrane Antigen (EMA), also known as Mucin 1 (MUC1), is a protein found on the surface of many types of epithelial cells and is widely distributed in epithelial tissues and tumors. This protein is a large cell surface mucoprotein, a high molecular weight glycoprotein, composed of two subunits: MUC1-N and MUC1-C.
What Epithelial Membrane Antigen Does
EMA supports cell defense against pathogens and participates in cell signaling processes. It is also involved in maintaining the structural integrity of epithelial layers and cell adhesion. EMA can interact with other molecules, such as E-cadherin and beta-catenin, influencing cellular interactions and differentiation.
Using EMA in Medical Diagnosis
EMA is a valuable diagnostic tool in medicine, particularly in pathology, where it functions as a biomarker. It helps pathologists determine the origin of abnormal cells or tumors and distinguish between different types of growths. Its presence on the surface of epithelial-derived tumors, such as primary or secondary carcinomas, makes it useful for identifying their epithelial nature.
Immunohistochemistry (IHC) is the common technique used to detect EMA in tissue samples. This method involves using antibodies that specifically bind to EMA, allowing its visualization in cells and tissues.
EMA is considered a broad-spectrum antibody, reacting against many types of adenocarcinomas. It can help differentiate between the origins of glandular organs. For instance, the use of EMA markers in conjunction with anti-cytokeratin antibodies is useful for characterizing cells of epithelial origin, while combining EMA with CD45 (LCA) can help identify cells of lymphoid origin.
Diseases Linked to EMA Expression
EMA expression is relevant for the diagnosis and classification of several medical conditions, particularly cancers. Meningiomas, which are tumors arising from the meninges surrounding the brain and spinal cord, consistently express EMA. This expression helps distinguish meningiomas from other tumors that might appear similar, such as schwannomas, which are typically EMA-negative. In some studies, EMA positivity in meningiomas has been as high as 96%.
In breast cancer, EMA is frequently expressed, with breast and skin adnexal tumors often showing strong positivity. EMA expression can also be observed in other adenocarcinomas, including those of the endometrium, kidney, thyroid, stomach, pancreas, lung, colon, ovary, prostate, and cervix, though often to a lesser degree.
EMA expression is also observed in malignant mesothelioma and can help distinguish it from reactive mesothelial hyperplasia. While EMA is expressed in both mesothelioma and metastatic adenocarcinoma, it is a useful marker for differentiating neoplastic mesothelium from non-neoplastic mesothelium. Studies have shown EMA positivity in a range of 58% to 100% in malignant mesothelioma cases.
Certain lymphomas, such as anaplastic large cell lymphoma (ALCL) and nodular lymphocyte-predominant Hodgkin lymphoma, can also express EMA. EMA may be observed in 50% to 95% of ALCL cases. This expression helps in the diagnostic classification of these lymphomas, especially in differentiating them from other types of non-Hodgkin’s lymphomas. EMA has also been found on reactive and neoplastic plasma cells.