EPITHELIAL MEMBRANE ANTIGEN IN HEMATOLYMPHOID NEOPLASMS - A REVIEW

The transmembrane glycoprotein of the breast mucin complex, or epithel ial membrane antigen (EMA), is encoded by the MUC1 gene, located on ch romosome 1 in 1q21-24 region. EMA expression as detected by anti-EMA a ntibodies 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 geneti c polymorphism. In hematolymphoid tissues, EMA is normally expressed b y plasma cells. The expression of EMA is conserved and probably height ened 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. Th e 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 lymph ocyte predominance Hodgkin's disease (nLPHD) and in anaplastic large c ell lymphomas (ALCL). EMA expression in Reed-Sternberg cells of classi c Hodgkin's disease (HD) is unusual. Although the differential express ion 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 an d correlate the differential glycosylation of the core proteins with b iologic behavior of lymphoid neoplasms, as is being currently attempte d for neoplasms of the glandular epithelium.