Wilms tumor 1/cytokeratin dual-color immunostaining reveals distinctive staining patterns in metastatic melanoma, metastatic carcinoma, and mesothelial cells in pleural fluids: an effective first-line test for the workup of malignant effusions

Our plain-English summary of Wilms tumor 1/cytokeratin dual-color immunostaining reveals distinctive staining patterns in metastatic melanoma, metastatic carcinoma, and mesothelial cells in pleural fluids: an effective first-line test for the workup of malignant effusions, by J.R. Conner, E.S. Cibas, J.L. Hornick, et al (Cancer Cytopathology, 2014).

The study

• Authors: J.R. Conner, E.S. Cibas, J.L. Hornick, X. Qian
• Journal: Cancer Cytopathology
• Published: 2014;122(8):586-95
• Cited by: 17 articles, as counted by NIH iCite
• Read it: PubMed · Publisher

Abstract

Background: The workup of a malignant effusion usually requires immunostaining with a panel of markers. Although nuclear Wilms tumor 1 (WT1) expression is widely used to detect tumors of ovarian and mesothelial origin, it is less well known that WT1 is also expressed in the cytoplasm of melanomas and mesenchymal tumors. Because to the authors' knowledge the diagnostic utility of cytoplasmic WT1 expression has not been explored to date, the usefulness of a WT1/AE1/AE3 dual-color immunostain in the workup of malignant effusions was evaluated.

Methods: A total of 86 pleural effusions, including 17 metastatic melanomas, 31 metastatic adenocarcinomas, 10 malignant mesotheliomas, 10 lymphoproliferative disorders, 5 metastatic sarcomas, and 13 benign specimens, were immunostained using a peroxidase-based brown chromogen for WT1 and an alkaline phosphatase-based red chromogen for AE1/AE3 on cell block sections.

Results: The majority of malignant effusions stained in 1 of 4 distinctive patterns: 1) all lung and breast adenocarcinomas demonstrated cytoplasmic AE1/AE3 expression without nuclear or cytoplasmic WT1 expression; 2) serous carcinomas of Müllerian origin, mesotheliomas, and benign mesothelial cells were positive for cytoplasmic AE1/AE3 as well as nuclear WT1; 3) melanomas, sarcomas, and a subset of plasma cell neoplasms were positive for cytoplasmic expression of WT1 but negative for AE1/AE3; and 4) large B-cell lymphomas and a subset of plasma cell neoplasms were negative for both markers.

Conclusions: A WT1/AE1/AE3 dual-color immunostain can reliably identify malignancy in pleural effusions and group malignant cells into discrete subsets, thereby narrowing the differential diagnosis. This simple double stain can be a cost-effective, first-line test in the workup of patients with malignant effusions.

© 2014 American Cancer Society.

In plain English

This laboratory study tested whether a two-color stain could help sort cells in fluid around the lungs (pleural effusions). The authors stained 86 archived pleural fluid samples from the in-house and consultation files of Brigham and Women's Hospital's cytopathology division, dated 2000 to 2013, for two markers: WT1 and the cytokeratin AE1/AE3. The samples included 10 malignant mesotheliomas, 13 benign samples, metastatic melanomas, carcinomas and sarcomas, and diffuse large B-cell lymphomas and plasma cell neoplasms. All 13 benign samples and all 10 mesotheliomas showed keratin in the cell body (cytoplasm) and WT1 in the nucleus. Serous carcinomas of Müllerian origin mostly showed this same pattern. All 11 breast carcinomas and all 10 lung adenocarcinomas showed keratin without WT1. All 17 melanomas lacked keratin but showed WT1 in the cytoplasm, as did all 4 angiosarcomas. None of 5 diffuse large B-cell lymphomas stained, and plasma cell neoplasms varied. The authors concluded the stain was effective as a first-line test. They noted it is not specific for any single tumor type, and that no reliable stain currently separates benign from malignant mesothelial cells. The article does not discuss asbestos.

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 diagnostic study: archived pleural fluid samples (cell blocks) were re-stained with a WT1/AE1/AE3 dual-color immunostain
• Who was studied: 86 pleural effusion samples from the in-house and consultation files of the Cytopathology Division, Brigham and Women's Hospital, 2000 to 2013. One cell block, a melanoma, was a consultation case whose preparation method was not specified. The samples comprised 17 metastatic melanoma, 10 metastatic lung adenocarcinoma, 11 metastatic breast adenocarcinoma, 10 metastatic serous carcinoma of Müllerian origin, 10 malignant mesothelioma, 5 diffuse large B-cell lymphoma, 5 plasma cell neoplasm, 4 metastatic epithelioid angiosarcoma, 1 metastatic rhabdomyosarcoma, and 13 samples negative for malignant cells. Samples read as suspicious or atypical were excluded.
• Exposure: No asbestos or other environmental or occupational exposure was studied. The study evaluated a laboratory stain: WT1 (brown) combined with the broad-spectrum cytokeratin AE1/AE3 (red).
• Main results:
  • Reactive (benign) mesothelial cells (13 of 13) and malignant mesothelioma (10 of 10) all showed diffuse cytoplasmic AE1/AE3 and diffuse nuclear WT1 staining. The two could not be told apart by this pattern.
  • Histiocytes were negative for both markers in all specimens examined.
  • All metastatic breast carcinomas (11 of 11) and lung adenocarcinomas (10 of 10) were positive for cytoplasmic AE1/AE3 and negative for WT1.
  • All 10 serous carcinomas of Müllerian origin were AE1/AE3 positive. For nuclear WT1, 6 showed diffuse staining (60%), 3 focal staining (30%), and 1 no staining (10%).
  • All 17 metastatic melanomas were negative for AE1/AE3 and nuclear WT1. They showed cytoplasmic WT1 that was diffuse in 15 of 17 (88%) and focal in 2 of 17 (12%). Melanin pigment complicated reading in 5 of the 17, and a reversed-color protocol confirmed cytoplasmic WT1 in those cases.
  • All 4 epithelioid angiosarcomas showed diffuse cytoplasmic WT1, and 1 also showed focal nuclear WT1. The single pleomorphic rhabdomyosarcoma showed strong WT1 in both nucleus and cytoplasm.
  • None of the 5 diffuse large B-cell lymphomas stained for either marker. Of the 5 plasma cell neoplasms, 1 showed diffuse cytoplasmic WT1, 1 showed focal WT1, and 3 showed no staining. AE1/AE3 was absent in all mesenchymal tumors and lymphoproliferative disorders.
• The authors' conclusion: The authors concluded that the WT1/AE1/AE3 double immunostain is effective in the first-line workup of pleural effusions. They added that further stains are often needed to confirm a tumor's origin.
• Limitations the authors state:
  • The authors stated that the test is not specific for any single tumor type.
  • Sarcomas and plasma cell neoplasms show the same cytoplasmic WT1 pattern as melanoma, which limits specificity.
  • No reliable immunostain currently distinguishes benign from malignant mesothelial cells. Both showed the same pattern in this study.
  • Only two sarcoma types were included, in a small sample.
  • A sample negative for both markers does not rule out cancer.

Topics

Medical terms in this study, explained in our Lexicon: Wilms Tumor 1 (WT-1), Carcinoma, Mesothelial Cells, Mesenchymal Tumor, Pleural Effusion, Adenocarcinoma, Malignant Mesothelioma, Sarcoma.

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