Sources/Clones
Accurate (E29), Biodesign, Biogenesis (2D5/11), Biogenex (E29, Mc-5), Bioprobe (HMFGP1.4), Chemicon, Dako (E29), Diagnostic Biosystems (E29), Immunon (polyclonal, E29), Immunotech (E29, E348KP), Medac, Novocastra, Oncogene (MC5), Seralab (HMFG/5/11IC, polyclonal), Serotec and Zymed (ZCE113).
Fixation/Preparation
Most antibodies are immunoreactive in fixed paraffin-embedded sections. Immunostaining is enhanced by proteolytic digestion or HIER, the latter producing less background staining.
Background
Antiepithelial membrane antigen (EMA) antibodies recognize a group of closely related high molecular weight transmembrane glycoproteins with a high carbohydrate content. The MUC1 gene, located on chromosome 1 in 1q21-24 region, encodes EMA. EMA is very similar to the human milk fat globule (HMFG). A heterogeneous population of HMFG proteins can be recovered from the aqueous phase of skimmed milk following extraction in chloroform and methanol. EMA is related to the high molecular weight glycoproteins of HMFG, especially to HMFG2 (Heyderman et al, 1985). Preparations of EMA reacted with polyclonal antibodies raised to delipidized HMFG with avid binding to wheat germ agglutinin and peanut agglutinin. A similar mucin-containing glycoprotein was solubilized from HMFG and labeled PAS-O because of reactivity for PAS (Shimuzu & Yamauchi, 1982). PAS-O and EMA represent closely allied glycoprotein moieties, with common antigenic determinants on both proteins. From a practical standpoint, patterns of immunoreactivity for EMA and HMFG are very similar (Strickler et al, 1987).
EMA reactivity is found in a wide variety of epithelial cells and their corresponding tumors. When present, immunoreactivity is usually limited to apical cell membranes in benign secretory epithelium and well-differentiated carcinomas such as those of the breast, but in poorly differentiated carcinomas, cytoplasmic staining is seen and there is loss of staining polarity in the cell membranes. Secretory epithelia and their fetal anlage that show EMA include eccrine sweat glands, sebaceous and apocrine glands. It is also expressed in salivary gland, exocrine pancreas, gastric and endometrium, bronchial glands, alveolar cells and the epithelium of bile ducts, stomach, bronchi, fallopian tube and vas deferens. In addition to glandular epithelium, EMA has also been demonstrated in non-secretory epithelia such as urothelium, renal distal and collecting tubules and syncytiotrophoblasts.
Applications
Despite the ready availability of anticytokeratin as a marker of epithelial differentiation, there is still widespread use of EMA as a marker of epithelial cells. This is fraught with inconsistencies. While EMA is generally not expressed by germ cells, normal hematolymphoid, mesenchymal, neural and neuroectodermal, it may be expressed by certain non-epithelial tissues such as fetal notochord, arachnoid granulations, ependyma, choroid plexus, epineural and perineural fibroblasts, histiocytes and plasma cells and their corresponding neoplasms. EMA is normally expressed by plasma cells and is conserved and even increased in plasma cell neoplasms and, by ultrastructural examination, has been located diffusely on the cell membranes and focally within rough endoplasmic reticulum. Neoplasms from earlier stage B-cell differentiation do not usually express EMA and in lymph node-based B-cell lymphomas, EMA is found mainly in diffuse large cell lymphomas and T cell-rich B-cell lymphomas. EMA is more frequently seen in T-cell neoplasms, occurring in about 20% of all T-cell lymphomas (Chittal et al, 1997). EMA expression in Reed-Sternberg cells is unusual although it is frequently found in the L&H cells of nodular lymphocyte-predominant Hodgkin's disease. EMA is also found in almost 50% of cases of anaplastic large cell lymphoma of CD 30 phenotype.
In our practice, staining for EMA is not generally employed as a marker of epithelial cells but more often for the identification of certain mesenchymal tumors including synovial sarcoma (Leong et al, 1997), anaplastic large cell lymphoma (CD 30+) and perineurioma (Li et al, 1996). The expression of EMA in chordoma serves to distinguish it from chondroma and chondrosarcoma (Gown & Leong, 1993; Jeffrey et al, 1995) and EMA is expressed in solitary fibrous tumors (Carneiro et al, 1996). EMA immunostaining may help identify ovarian granulosa cell tumors from tumors that mimic their various histological patterns. While keratin may be expressed in granulosa cell tumors, the absence of EMA and immunoreactivity for smooth muscle actin allows distinction from primary and metastatic carcinomas (Costa et al, 1994).
Immunostaining for EMA is a valuable adjunct to the examination of effusions and biopsies for malignant mesothelioma. By ultrastructural examination EMA has been demonstrated exclusively on the long microvillous surfaces of the tumors cells with virtually no cytoplasmic labeling (Van Der Kwast et al, 1987). These findings have been transposed to cytologic preparations and biopsies and careful staining for EMA employing clone E29 shows membranous labeling of malignant mesothelial cells and demonstrates the long microvilli characteristic of the tumor. In contrast, adenocarcinomas display diffuse cytoplasmic staining, with or without membranous enhancement, but long microvilli are not seen (Leong et al, 1990).
Comments
For diagnostic applications we prefer to use anti-EMA (clone E29) instead of HMFG, especially as both antigens have very similar tissue distribution.
References
•Carneiro SS, Scheithauer BW, Nascimento AG et al 1996. Solitary fibrous tumor of the meninges: a lesion distinct from fibrous meningioma. A clinicopathologic and immunohistological study. American Journal of Clinical Pathology 106: 217-224.
•Chittal S, Saati TA, Delsol G 1997. Epithelial membrane antigen in hematolymphoid neoplasms. A review. Applied Immunohistochemistry 5: 203-215.
•Costa MJ, De Rose PB, Rotla LM et al 1994. Immunohistochemical phenotype of ovarian granulosa cell tumors: absence of epithelial membrane antigen has diagnostic value. Human Pathology 25: 60-66.
•Gown AM, Leong AS-Y 1993. Immunohistochemistry of `solid' tumors: poorly differentiated round cell and spindle cell tumors II. IN: Leong AS-Y (ed) Applied immunohistochemistry for the surgical pathologist. London: Edward Arnold pp 74-109.
•Heyderman E, Strudley I, Powell G et al 1985. A new monoclonal antibody to epithelial membrane antigen (EMA) E29. A comparison of its immunocytochemical reactivity with polyclonal anti-EMA antibodies and with another monoclonal antibody HMFG-2. British Journal of Cancer 52: 355-361.
•Jeffrey PB, Biava CG, Davis RL 1995. Chondroid chordoma. A hyalinized chordoma without cartilaginous differentiation. American Journal of Clinical Pathology 103: 271-279.
•Leong AS-Y, Parkinson R, Milios J 1990. "Thick" cell membranes revealed by immunocytochemical staining: a clue to the diagnosis of mesothelioma. Diagnostic Cytopathology 6: 9-13. staining: a clue to the diagnosis of mesothelioma. Diagnostic Cytopathology 6: 9-13.
•Leong AS-Y, Wick MR, Swanson PE 1997. Immunohistology and electron microscopy of anaplastic and pleomorphic tumors. Cambridge: Cambridge University Press pp 155-157.
•Li D, Schauble, Moll C, Fisch U 1996. Intratemporal facial nerve perineurioma. Laryngoscope 106: 328-333.
•Shimizu M, Yamauchi K 1982. Isolation and characterization of mucin-like glycoprotein in human milk fat globule membrane. Journal of Biochemistry 91: 515-524.
•Strickler JG, Herndier BG, Rowe RV 1987 Immunohistochemical staining in malignant mesotheliomas. American Journal of Clinical Pathology 88: 610-614.
•Van Der Kwast TH, Versnel MA, Delahaye M et al 1987. Expression of epithelial membrane antigen on malignant mesothelial cells. An immunocytochemical and immunoelectron microscopic study. Acta Cytologica 32: 169-174.
Bibliografía
Manual of diagnostic antibodies for immunohistology / Anthony S.-Y. Leong, Kumarasen Cooper, F. Joel W.-M. Leong.
Accurate (E29), Biodesign, Biogenesis (2D5/11), Biogenex (E29, Mc-5), Bioprobe (HMFGP1.4), Chemicon, Dako (E29), Diagnostic Biosystems (E29), Immunon (polyclonal, E29), Immunotech (E29, E348KP), Medac, Novocastra, Oncogene (MC5), Seralab (HMFG/5/11IC, polyclonal), Serotec and Zymed (ZCE113).
Fixation/Preparation
Most antibodies are immunoreactive in fixed paraffin-embedded sections. Immunostaining is enhanced by proteolytic digestion or HIER, the latter producing less background staining.
Background
Antiepithelial membrane antigen (EMA) antibodies recognize a group of closely related high molecular weight transmembrane glycoproteins with a high carbohydrate content. The MUC1 gene, located on chromosome 1 in 1q21-24 region, encodes EMA. EMA is very similar to the human milk fat globule (HMFG). A heterogeneous population of HMFG proteins can be recovered from the aqueous phase of skimmed milk following extraction in chloroform and methanol. EMA is related to the high molecular weight glycoproteins of HMFG, especially to HMFG2 (Heyderman et al, 1985). Preparations of EMA reacted with polyclonal antibodies raised to delipidized HMFG with avid binding to wheat germ agglutinin and peanut agglutinin. A similar mucin-containing glycoprotein was solubilized from HMFG and labeled PAS-O because of reactivity for PAS (Shimuzu & Yamauchi, 1982). PAS-O and EMA represent closely allied glycoprotein moieties, with common antigenic determinants on both proteins. From a practical standpoint, patterns of immunoreactivity for EMA and HMFG are very similar (Strickler et al, 1987).
EMA reactivity is found in a wide variety of epithelial cells and their corresponding tumors. When present, immunoreactivity is usually limited to apical cell membranes in benign secretory epithelium and well-differentiated carcinomas such as those of the breast, but in poorly differentiated carcinomas, cytoplasmic staining is seen and there is loss of staining polarity in the cell membranes. Secretory epithelia and their fetal anlage that show EMA include eccrine sweat glands, sebaceous and apocrine glands. It is also expressed in salivary gland, exocrine pancreas, gastric and endometrium, bronchial glands, alveolar cells and the epithelium of bile ducts, stomach, bronchi, fallopian tube and vas deferens. In addition to glandular epithelium, EMA has also been demonstrated in non-secretory epithelia such as urothelium, renal distal and collecting tubules and syncytiotrophoblasts.
Applications
Despite the ready availability of anticytokeratin as a marker of epithelial differentiation, there is still widespread use of EMA as a marker of epithelial cells. This is fraught with inconsistencies. While EMA is generally not expressed by germ cells, normal hematolymphoid, mesenchymal, neural and neuroectodermal, it may be expressed by certain non-epithelial tissues such as fetal notochord, arachnoid granulations, ependyma, choroid plexus, epineural and perineural fibroblasts, histiocytes and plasma cells and their corresponding neoplasms. EMA is normally expressed by plasma cells and is conserved and even increased in plasma cell neoplasms and, by ultrastructural examination, has been located diffusely on the cell membranes and focally within rough endoplasmic reticulum. Neoplasms from earlier stage B-cell differentiation do not usually express EMA and in lymph node-based B-cell lymphomas, EMA is found mainly in diffuse large cell lymphomas and T cell-rich B-cell lymphomas. EMA is more frequently seen in T-cell neoplasms, occurring in about 20% of all T-cell lymphomas (Chittal et al, 1997). EMA expression in Reed-Sternberg cells is unusual although it is frequently found in the L&H cells of nodular lymphocyte-predominant Hodgkin's disease. EMA is also found in almost 50% of cases of anaplastic large cell lymphoma of CD 30 phenotype.
In our practice, staining for EMA is not generally employed as a marker of epithelial cells but more often for the identification of certain mesenchymal tumors including synovial sarcoma (Leong et al, 1997), anaplastic large cell lymphoma (CD 30+) and perineurioma (Li et al, 1996). The expression of EMA in chordoma serves to distinguish it from chondroma and chondrosarcoma (Gown & Leong, 1993; Jeffrey et al, 1995) and EMA is expressed in solitary fibrous tumors (Carneiro et al, 1996). EMA immunostaining may help identify ovarian granulosa cell tumors from tumors that mimic their various histological patterns. While keratin may be expressed in granulosa cell tumors, the absence of EMA and immunoreactivity for smooth muscle actin allows distinction from primary and metastatic carcinomas (Costa et al, 1994).
Immunostaining for EMA is a valuable adjunct to the examination of effusions and biopsies for malignant mesothelioma. By ultrastructural examination EMA has been demonstrated exclusively on the long microvillous surfaces of the tumors cells with virtually no cytoplasmic labeling (Van Der Kwast et al, 1987). These findings have been transposed to cytologic preparations and biopsies and careful staining for EMA employing clone E29 shows membranous labeling of malignant mesothelial cells and demonstrates the long microvilli characteristic of the tumor. In contrast, adenocarcinomas display diffuse cytoplasmic staining, with or without membranous enhancement, but long microvilli are not seen (Leong et al, 1990).
Comments
For diagnostic applications we prefer to use anti-EMA (clone E29) instead of HMFG, especially as both antigens have very similar tissue distribution.
References
•Carneiro SS, Scheithauer BW, Nascimento AG et al 1996. Solitary fibrous tumor of the meninges: a lesion distinct from fibrous meningioma. A clinicopathologic and immunohistological study. American Journal of Clinical Pathology 106: 217-224.
•Chittal S, Saati TA, Delsol G 1997. Epithelial membrane antigen in hematolymphoid neoplasms. A review. Applied Immunohistochemistry 5: 203-215.
•Costa MJ, De Rose PB, Rotla LM et al 1994. Immunohistochemical phenotype of ovarian granulosa cell tumors: absence of epithelial membrane antigen has diagnostic value. Human Pathology 25: 60-66.
•Gown AM, Leong AS-Y 1993. Immunohistochemistry of `solid' tumors: poorly differentiated round cell and spindle cell tumors II. IN: Leong AS-Y (ed) Applied immunohistochemistry for the surgical pathologist. London: Edward Arnold pp 74-109.
•Heyderman E, Strudley I, Powell G et al 1985. A new monoclonal antibody to epithelial membrane antigen (EMA) E29. A comparison of its immunocytochemical reactivity with polyclonal anti-EMA antibodies and with another monoclonal antibody HMFG-2. British Journal of Cancer 52: 355-361.
•Jeffrey PB, Biava CG, Davis RL 1995. Chondroid chordoma. A hyalinized chordoma without cartilaginous differentiation. American Journal of Clinical Pathology 103: 271-279.
•Leong AS-Y, Parkinson R, Milios J 1990. "Thick" cell membranes revealed by immunocytochemical staining: a clue to the diagnosis of mesothelioma. Diagnostic Cytopathology 6: 9-13. staining: a clue to the diagnosis of mesothelioma. Diagnostic Cytopathology 6: 9-13.
•Leong AS-Y, Wick MR, Swanson PE 1997. Immunohistology and electron microscopy of anaplastic and pleomorphic tumors. Cambridge: Cambridge University Press pp 155-157.
•Li D, Schauble, Moll C, Fisch U 1996. Intratemporal facial nerve perineurioma. Laryngoscope 106: 328-333.
•Shimizu M, Yamauchi K 1982. Isolation and characterization of mucin-like glycoprotein in human milk fat globule membrane. Journal of Biochemistry 91: 515-524.
•Strickler JG, Herndier BG, Rowe RV 1987 Immunohistochemical staining in malignant mesotheliomas. American Journal of Clinical Pathology 88: 610-614.
•Van Der Kwast TH, Versnel MA, Delahaye M et al 1987. Expression of epithelial membrane antigen on malignant mesothelial cells. An immunocytochemical and immunoelectron microscopic study. Acta Cytologica 32: 169-174.
Bibliografía
Manual of diagnostic antibodies for immunohistology / Anthony S.-Y. Leong, Kumarasen Cooper, F. Joel W.-M. Leong.
