Epithelial membrane antigen in hematolymphoid neoplasms - A review

The transmembrane glycoprotein of the breast mucin complex, or epithelial membrane antigen (EMA), is encoded by the MUC1 gene, located on chromosome 1 in 1q21-24 region. EMA expression as detected by anti-EMA antibodies is found in many epithelial cells other than the breast and its neoplasms, but the epitopes recognized are different depending on the antibody used because of different glycosylation levels and genetic polymorphism. In hematolymphoid tissues, EMA is normally expressed by plasma cells. The expression of EMA is conserved and probably heightened in plasma cell neoplasms, whereas neoplasms from earlier stage B-cell differentiation are not usually associated with the expression of EMA. Within the lymph node-based B-cell lymphomas, the EMA is mainly expressed by diffuse large B-cell-and T-cell-rich B-cell lymphomas. The expression of EMA is more frequent in T-cell malignancies, occurring in about 20% of all T-cell lymphomas. The most frequent expression of EMA is recorded in lymphocytic and histiocytic cells of nodular lymphocyte predominance Hodgkin's disease (nLPHD) and in anaplastic large cell lymphomas (ALCL). EMA expression in Reed-Sternberg cells of classic Hodgkin's disease (HD) is unusual. Although the differential expression of EMA within lymphoid neoplasms may be of diagnostic assistance, clear biologic significance of EMA expression or MUC1 gene activation in lymphomas has yet to emerge. To this end, it is important to study the patterns of activation of the MUC1 gene by different antibodies and correlate the differential glycosylation of the core proteins with biologic behavior of lymphoid neoplasms, as is being currently attempted for neoplasms of the glandular epithelium.