Use of antisera to epithelial membrane antigen for the cytodiagnosis of malignancy in serous effusions

Our plain-English summary of Use of antisera to epithelial membrane antigen for the cytodiagnosis of malignancy in serous effusions, by A. To, D.V. Coleman, D.P. Dearnaley, et al (Journal of Clinical Pathology, 1981).

The study

• Authors: A. To, D.V. Coleman, D.P. Dearnaley, M.G. Ormerod, K. Steele, A.M. Neville
• Journal: Journal of Clinical Pathology
• Published: 1981;34(12):1326-32
• Cited by: 99 articles, as counted by NIH iCite
• Read it: PubMed · Publisher · Free full text

Abstract

A new human antigen, designated epithelial membrane antigen (EMA), has recently been described on surface membranes of a wide variety of normal epithelium but not on connective tissue cells. The antigen is only weakly expressed on normal or reactive mesothelium. Increased expression of the antigen has been observed in most neoplasms of epithelial origin and in malignant mesothelioma. We have investigated the possibility of using this difference in the expression of the antigen to distinguish between mesothelial cells and malignant cells in cytological smears of serous effusions. This distinction cannot always be made on morphological grounds alone and problems of differential diagnosis are encountered in about 15% of all specimens of serous effusions sent for cytological examination. Using antisera to EMA we have applied an indirect immunoalkaline phosphatase technique to alcohol-fixed smears prepared from serous effusions and have found that intense staining of the antigen is confined to effusions from patients in whom there is either clinical or cytological evidence of malignancy. The technique proved to be especially useful in cytologically equivocal cases, where there were problems of differential diagnosis.

In plain English

This laboratory study tested whether staining for epithelial membrane antigen (EMA) could help tell cancer cells from mesothelial cells in pleural and peritoneal fluid. The authors examined 127 effusions (86 pleural, 41 ascitic) from 100 patients. These were routine specimens sent to the cytology laboratory at St Mary's Hospital, London, in 1980, plus others received from two other hospitals. Of these patients, 70 had malignant disease and 30 had no evidence of it. Of 77 effusions from patients with proven epithelial or mesothelial cancer, 66 (86%) showed EMA. Weak staining was also seen in nine effusions from patients without cancer, so the authors judged it could not be used as a sign of malignancy. Strong 'dense central' staining appeared in 42 effusions: 41 from patients with proven cancer and one from an 81-year-old woman with pneumonia in whom cancer could not be ruled out. Of two effusions from patients with cytological evidence of mesothelioma, one stained strongly and one more weakly. All six lymphoma effusions were EMA-negative. The authors concluded that strong dense central staining appeared specific and sensitive for malignant epithelial cells, while noting that confirmation by later studies was needed.

We wrote this plain-English summary from the full article with the help of AI, and a second AI model checked each sentence against the article. It is not the authors' wording; the abstract and the article are their own account.

What the study did and found

• Design: Diagnostic laboratory study comparing EMA immunostaining of effusion smears with conventional cytological (morphological) diagnosis and mucin staining
• Who was studied: 127 effusions (86 pleural, 41 ascitic) from 100 patients. These were all adequate specimens sent routinely to the St Mary's Hospital, London, cytology laboratory between 1 January and 30 September 1980, plus specimens received from the Royal Marsden Hospital and St Bartholomew's Hospital. 70 patients had malignant disease (including 2 with mesothelioma and 4 with lymphoma), and 30 had no evidence of malignancy.
• Exposure: Not an exposure study. The factor examined was a diagnostic test: indirect immunoalkaline phosphatase staining of alcohol-fixed smears with rabbit antiserum to epithelial membrane antigen. No asbestos or fiber exposure was assessed.
• Main results:
  • Conventional cytology gave a firm diagnosis of malignancy in 62 of the 127 (49%) effusions, a suspicious report in 15 (12%), and a negative report in 50 (39%).
  • 66 of 77 effusions (86%) from patients with proven epithelial or mesothelial malignancy expressed EMA. Of these 66, 25 showed only weak (rim/diffuse) staining.
  • Weak EMA staining was also seen in nine effusions from patients without malignant disease, so the authors stated that the weak pattern cannot be used as a criterion for malignancy.
  • Strong dense central staining occurred in 42 effusions: 41 from patients with proven malignant disease and one from an 81-year-old woman with pneumonia whose effusion contained very suspicious cells.
  • Two effusions came from patients with cytological evidence of mesothelioma, one of them confirmed histologically. The abnormal mesothelial cells stained strongly for EMA in one specimen and more weakly in the other.
  • All six effusions from four patients with lymphoma were negative for EMA.
  • Among the 15 cytologically suspicious effusions, EMA staining (absent in four, strong in four) aided diagnosis in eight (53%).
• The authors' conclusion: The authors concluded that their data suggest strong dense central EMA staining, used as the sole criterion for malignancy, is both specific and sensitive for detecting malignant epithelial cells in serous effusions. They added that it may be especially valuable alongside morphological diagnosis in equivocal cases.
• Limitations the authors state:
  • The authors noted that no available cell marker is tumour-specific, so some staining of mesothelium may be expected.
  • The authors stated that subsequent studies would need to confirm that strong EMA staining is specific for malignancy.
  • The authors noted that results depend on strict standardisation of antiserum dilutions and incubation times, and that the antigen does not survive prolonged storage of ethanol-fixed smears at room temperature.

Topics

The National Library of Medicine indexes this study under subjects our site covers: Pleural plaques and thickening.

Medical terms in this study, explained in our Lexicon: Epithelial Membrane Antigen (EMA), Epithelium, Mesothelium, Neoplasm, Mesothelioma, Mesothelial Cells, Differential Diagnosis.

Related studies

• Utility of HBME-1 immunostaining in serous effusions — V. Ascoli, C. Carnovale-Scalzo, et al. (1997)
• Calretinin. A selective marker of normal and neoplastic mesothelial cells in serous effusions — M.C. Barberis, M. Faleri, et al. (1997)
• The distinction of adenocarcinoma from malignant mesothelioma in cell blocks of effusions: the role of routine mucin histochemistry and immunohistochemical assessment of carcinoembryonic antigen, keratin proteins, epithelial membrane antigen, and milk fat globule-derived antigen — E.S. Cibas, J.M. Corson, et al. (1987)
• Value of immunocytochemistry in the study of malignant effusions — M.R. Mason, C.W. Bedrossian, et al. (1987)
• Diagnostic problems in serous effusions — C.W. Bedrossian (1998)
• Lectin binding properties of cells from serous effusion and peritoneal washing specimens — P.W. Shield (1989)

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