Melan A (A103) is not a marker of mesothelioma

Our plain-English summary of Melan A (A103) is not a marker of mesothelioma, by N.G. Ordóñez, S.S. Shen, M. Zenali, et al (Applied Immunohistochemistry & Molecular Morphology, 2013).

The study

• Authors: N.G. Ordóñez, S.S. Shen, M. Zenali, M.T. Deavers
• Journal: Applied Immunohistochemistry & Molecular Morphology
• Published: 2013;21(2):181-4
• Cited by: 2 articles, as counted by NIH iCite
• Read it: PubMed · Publisher

Abstract

Although a large number of immunohistochemical markers have been proven to be valuable in the differential diagnosis between epithelioid mesotheliomas and metastatic carcinomas involving the serosal membrane, no single antibody has been found that is absolutely sensitive and/or specific in making this distinction. A recent study reported melan A positivity in all 12 of the epithelioid mesotheliomas stained with a melan A antibody (clone A103). To fully determine the practical value of this antibody for assisting in the differential diagnosis of mesotheliomas, we investigated the expression of melan A (A103) in 40 mesotheliomas (27 epithelioid, 6 sarcomatoid, and 7 biphasic), 10 lung adenocarcinomas, and 10 serous carcinomas of the ovary. None of the mesotheliomas, lung adenocarcinomas, or serous carcinomas of the ovary were melan A (A103) positive. Similar staining results were observed in the 20 mesotheliomas immunostained in another institution using the same antibody clone from a different commercial source. On the basis of these results, it is concluded that in contrast to the initial report, melan A (A103) is not expressed in mesotheliomas and therefore, immunostaining with this antibody has no utility in the diagnosis of mesothelioma. The possible cause of the discrepancies between the results obtained in the present investigation and those of the initial study is discussed.

In plain English

This laboratory study tested whether a stain called melan A (antibody clone A103) helps pathologists identify mesothelioma. An earlier report by Zenali and colleagues had described 12 epithelioid mesotheliomas as positive for this stain. The authors stained archived tumor tissue from the University of Texas M.D. Anderson Cancer Center: 40 mesotheliomas (27 epithelioid, 6 sarcomatoid and 7 biphasic), 10 lung adenocarcinomas and 10 serous carcinomas of the ovary. They also stained the same 12 cases from the earlier report. They used A103 antibody from the supplier Novocastra. None of these tumors stained positive, while a melanoma used as a check sample did. A second laboratory stained 20 pleural mesotheliomas with A103 antibody from the supplier Ventana, and all 20 were negative. The authors believed the most probable cause of the disagreement was that the earlier study used antibody from a different supplier (Lab Vision). The authors concluded that melan A (A103) is not expressed in mesotheliomas and that the earlier positive results most likely reflected a false-positive reaction of that antibody. The study did not examine asbestos exposure.

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: Laboratory immunohistochemistry (tissue staining) study of archived tumor samples, re-examining an earlier report
• Who was studied: Archived tumor tissue from M.D. Anderson Cancer Center: 40 mesotheliomas (27 epithelioid, 6 sarcomatoid, 7 biphasic), 10 lung adenocarcinomas and 10 serous carcinomas of the ovary, plus the 12 epithelioid mesotheliomas from the earlier Zenali report. A second laboratory stained 20 pleural mesotheliomas. Dates of the cases are not given.
• Exposure: Not an asbestos exposure study. What was tested was staining with the A103 anti-melan A antibody, from Novocastra in the main laboratory and from Ventana in a second laboratory.
• Main results:
  • None of the 40 mesotheliomas, 10 lung adenocarcinomas or 10 serous ovarian carcinomas reacted with the Novocastra A103 antibody.
  • The melanoma used as a positive control stained strongly.
  • The 12 epithelioid mesotheliomas previously reported by Zenali et al as melan A (A103) positive showed no expression when restained in this study.
  • Restaining of those 12 earlier cases found no melan A expression.
  • All 20 pleural mesotheliomas stained in a second laboratory with the Ventana A103 antibody were negative.
  • The authors believed the different commercial source of the antibody used in the earlier study (Lab Vision) was the most probable cause of the discrepancy.
• The authors' conclusion: The authors concluded that melan A (A103) is not expressed in mesotheliomas, and that the positivity in the earlier study most likely represented a false-positive reaction of the antibody used there.

Topics

The National Library of Medicine indexes this study under subjects our site covers: Lung cancer, Mesothelioma, Ovarian cancer.

Medical terms in this study, explained in our Lexicon: Mesothelioma, Differential Diagnosis, Epithelioid, Carcinoma, Sarcomatoid, Biphasic Mesothelioma, Lung Adenocarcinoma.

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