A WT1-positive pleural neoplasm. Is it always a mesothelioma?: Diagnostic pitfall of WT1 immunohistochemistry in pleural neoplasm

Our plain-English summary of A WT1-positive pleural neoplasm. Is it always a mesothelioma?: Diagnostic pitfall of WT1 immunohistochemistry in pleural neoplasm, by G. Gaggero, D. Taietti, M. Concardi, et al (African Journal of Thoracic and Critical Care Medicine, 2023).

The study

• Authors: G. Gaggero, D. Taietti, M. Concardi, M. Mora
• Journal: African Journal of Thoracic and Critical Care Medicine
• Published: 2023;29(3):1-2
• Type of article: Editorial
• Read it: PubMed · Free full text

In plain English

This was a short case report by pathologists in Italy. It described a 78-year-old woman with thickening of the lining of one lung (unilateral pleural thickening) and nodules within the lung. A PET scan showed uptake in the pleura and the peritoneum (the lining of the abdomen). A pleural biopsy showed a cancer made of epithelioid cells, mostly solid with some papillary areas. Stains on the tissue were positive for CK7 and WT1. They were negative for TTF1 and Napsin, which the authors said ruled out a lung origin, and negative for calretinin, CK5/6 and D2-40, which they said ruled out a mesothelial nature. Further stains were positive for PAX8, CA125, p53 and p16, pointing to a serous cancer. Radiological and gynaecological investigation found no masses in the uterus, tubes or ovaries. The authors judged the most likely diagnosis to be a rare primary peritoneal serous carcinoma. They warned that a positive WT1 stain should not be read apart from the other stains, because doing so could lead to a misdiagnosis of mesothelioma. The report did not mention 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: case report (single patient, short image-based report)
• Who was studied: one 78-year-old woman with unilateral pleural thickening and nodules within the lung; the authors were at hospitals and a university in Italy; no dates given
• Exposure: not reported; the article gives no asbestos or other exposure history
• Main results:
  • A PET scan showed uptake in the pleura and the peritoneum
  • The pleural biopsy showed a cancer of epithelioid cells, mostly solid with a smaller papillary part, with several mitoses
  • First stain panel: positive for CK7 and WT1; negative for TTF1, Napsin, calretinin, CK5/6 and D2-40
  • The authors stated that negative TTF1 and Napsin ruled out a lung origin
  • The authors stated that negative calretinin, CK5/6 and D2-40 also ruled out a mesothelial nature
  • An expanded stain panel aimed at a serous cancer was positive for PAX8, CA125, p53 and p16
  • Radiological and gynaecological investigation found no uterine or tubo-ovarian masses
  • The authors judged the most likely diagnosis to be a rare primary peritoneal serous carcinoma, taking the peritoneal PET uptake into account
• The authors' conclusion: The authors concluded that a positive WT1 stain in a pleural tumour should not be interpreted apart from the rest of the stain results, because doing so could lead to a misdiagnosis of mesothelioma

Topics

Medical terms in this study, explained in our Lexicon: Neoplasm, Mesothelioma, Immunohistochemistry.

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• Utility and pitfalls of immunohistochemistry in the differential diagnosis between epithelioid mesothelioma and poorly differentiated lung squamous cell carcinoma — K. Kushitani, V.J. Amatya, et al. (2017)
• Immunohistochemistry: applications to the evaluation of lung and pleural neoplasms: part 2 — H. Mani, D.S. Zander (2012)
• Immunoreactivity for calretinin and keratins in desmoid fibromatosis and other myofibroblastic tumors: a diagnostic pitfall — S. Barak, Z. Wang, et al. (2012)
• Peritoneal mesothelial hyperplasia associated with gynaecological disease: a potential diagnostic pitfall that is commonly associated with endometriosis — R. Oparka, W.G. McCluggage, et al. (2011)

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